MARCH 30, 1900.]

INSTITUTION OF MECHANICAL ENGINEER .

TING of the Inst.itution of Mechanical A. !BE was held on the evening of Thursday of Engmee~s March 22. In the regrettable absence las~i~William White, the President. of the .Insti-

of . Mr J Hartley Wicksteed, VICe-Prestdent, tutlOn, . . . w kste d d th

d the chatr Mr. 1c e opene e pro-occduple by readin.g a letter from Sir William White cee tngs b h ta Th' hich had been recet ved y t e sec re ry. . lS w expressed the great regret of the Prestdent le1ttter m g to ill-health he was unable to attend the t ta ow . 'd t tl .

t. of the Counctl or to prest e a 1e evenmg mee mg h t t' g this regret betng t e grea er as many ~:~:O~s in connection with the arrangements for

E N G I N E E RI N G. health was such that he had been directed by his medical advisers to abstain from all extra work for some time. Under these circumstances-circum-stances which might cause serious inconvenience at the present juncture- he desired to place himself un-reservedly in the hands of the Council to make such arrangements as they considered best for the interests of the Institution. Commenting on this, Mr. Wicksteed said that the Council were unani-mous in their decision that they should wish Sir William White to retain the position of President, even although he might not be able to attend the tneetings for some little time.

PowER HAMMERS AND PNEUMA.'l:Io TooLS. It will be remembered that at the h.st monthly

meeting of the Institution two papers were read

,, Little Giant" H igh Speed Rotary Drill.

A

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Fl9. 7.

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' I

Section ou 2-2. . ..

Fl.fj . q . Sectio11 on 4-4 .

the ensuing summer meeting of the Institution re-quired special attention, owing to its being in-tsnded to combine with that meeting a reception of the me m hers of the American Society of M echa-n~cal ~n~neers, who were about to visit England. Str. '\Yilliam went on to state that, acting on the dectston of the Council at their previous meeting, he had conferred with the President of the Institu-tion of Civil Engineers, and as a result it had been a;ranged that the summer meeting of the Institu-tton of ~echanical Engineers should be held in London m the last week in June next, and the Grand Hall of the Hotel Cecil had been engaged for the annual dinner on June 27.

The concluding portion of Sir William White's letter stated that unfortunately the condition of his

I.

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Sections through Valve.

E

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Fig .3 Section on 3-3.

Fig . 5 . Section ou 5-5. 0

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and partly discussed : these were '' Improvements in the Longworth Power Hammer," by Mr. Ernest Samuelson, of Ban bury ; and ''Portable Pneumatic Tools,': by Mr. Ewart C. Amos, of London. The discussion was adjourned by Mr. Wicksteed, who occupied the chair on the last occasion also, and on Thursday, the 22nd inst., the whole evening was devoted to the further consideration of these two papers.

Mr. Wicks teed opened the discussion by giving a brief 1es-ume of what was said at the former meet-ing, and was reported in our issue of March 2 last (see page 280 ante). Before the discussion was opened, Mr. Wicksteed requested Mr. Amos to make certain additions to his paper.

Mr . . Amoa, in reply, Faid that he _would give a

brief description of the "Little Giant " high-speed drill to which reference was made at the last meeting. Since then a new plate illustrating the drill in detail has been added to the paper and was in the hands of members. By reference to the illustrations which we reproduce herewith, it will be seen th~t this drill is provided with a main casing containing the mechanism. The l~tter c~nsists chiefly of three cylinders, each provided Wit.h piston valves and rotating round a fixed ecce~tnc and fixed crankpin. Live air having been admitted by actuating the admission valve, shown in the left-hand portion of the top figure, passes through a port as shown by the arrows into the valve bushing, and from thence into the cylinders. The effect of the compressed air acting on each piston in turn cau~es the cylinder to rotate about the fixed crankpm, whilst the fixed eccentric regulates the valves for. the proper admission of air to each cylinder . Attached to the bottom of the cylinder castings is a pinion which engages through two idlers with an internally-toothed wheel forming part of the drill-holder, and thus rotary motion is imparted to the drill bit. This machine, the speaker said, will attain a speed of about 1400 revolutions per minute. The chief advantage claimed for it is that it com-prises a high-speed engine with a minimum con-sumption of air, and this is obtained by employing the stationary eccentric referred to, in combina-tion with the piston valves, thus securing the proper cutoff of the air supply. It was further pointed out that both the live air and the exhaust pass through suitable ports, and are thus prevented from surrounding the working parts as in some other drills of this type. In the description given in the speaker's paper of the '' Little Giant" portable air .drill, it was stated that it was also fitted with a reversing arrange-ment, although not shown on the diagram. In the absence of this it was somewhat difficult to clearly describe the mechanism in detail. The speaker stated, however, that when the drill was so fitted, and handle takes the J?lace of the star centre (see Fig. 22, page 365 wnte), by revolving this handle a valve placed in the main pressure chamber reverses the direction taken by the air when entering the valve bushing, suitable ports being also provided. The drill when t hus fitted is capable of dealing with all kinds of work in which reversing is necessary, such as tapping, tube expanding, wood boring, &c. Mr. Amos also called attention to photographs of the " Little Giant '' drill, doing special work at the carriage department of the London and North-Western Railway at W olverton. By these it was seen that these machines were driving special saw bits for the purpose of cutting out the lamp holes and openings for the heating apparatus in railway carriages. This, it was stated, was the first appli-cation of the kind. Another diagram to which attention was called illustrated the Boyer long-stroke hammer. This differed from the Boy er hammer already described and illustrated in that it was provided with two hollow cylindrical valves, one at either end of the working cylinder. These valves automatically controlled the admission and exhaust of the air at either end of the piston through suitable ports, their object being to secure a much longer stroke to the striking piston than wa~ possible with one controlling valve. Another distinctive feature was that the machine would be inoperative except when pressed up to its work. The diagram showed a hammer with a stroke of 9 in., capable of giving a very powerful blow, and this type of hammer is doing good work in connection with hand riveting.

Mr. Simpson, of Pimlico, said that in their works they used pneumatic tools to a consider-able extent; in reckoning the relative advantages of the power hammer and the steam hammer t he short stroke of the steam hammer should be taken into account in the comparison. And, more-over, the exhaust from the steam hammer should be taken to a condenser. He had thought of put-ting down a power hammer but found that the steam hammer gave a greater range of work. He would suggest t hat it would be an advantage if steam hammers were fitted with smaller steam pipes, and that the steam should be superheated. In regard to pneumatic tools their experience was wholly with the Boyer hammer. The speaker had caused to be placed on the walls of the theatre a number of photographs illustrating the uses to which they put this machine. They had found it very handy in cleaning up castings, especially in the brass foundry, where the pneumatic hammer led to a great saving in the wages of trimmers.

he n1en in the foundry did not take to it very readily, objecting to the manner in which it jarred them in use. His firm had, however, found that younger 1nen did n ot experience the same un-pleasant result, and they were increasing the nu m her of machines of this class. They found a drill with compressed air gave better results than one worked with the Stow flexible shafting or by a ratchet. In one position they had found the use of the compressed air drill of the greatest benefit. In a deep well holes had to be drilled in some iron-work, so they had rigged up the W estinghouse air compressor and found it very easy to take the pipes down the well and carry on the work. They used small pneumatic drills for the holes in cylinder lag-ging and other light work; here there was a great saving, for it was not easy to take the work to the ordinary machines. No doubt further experience was needed before a definite statement could be made as to the ultimate economy of this class of machinery. So far they had had very little trouble, but it would be necessary to ascertain what would be the cost of repairs extending over a number of years. They had also used the air hoists described with great advantage and found them excellent for placing work in the lathe. Among the supplemental uses of compressed air might be mentioned the spraying of whitewash over walls, in this way considerable time and expense was saved, as compared to the older methods. They were satisfied from the ex-perience already gained that before long they would have to increase the number of their pneumatic tools.

Mr. Wicks teed said that at the Great Northern Rail way 'Vorks at Doncaster he had seen the best installation of pneumatic machinery that he had met with, and he would call on Mr. Ivatt, the locomotive superintendent of the railway company, to give his experience. In response to this invitation, Mr. Ivatt stated that he had gone in smnewhat largely for pneumatic machinery at Doncaster. He could give no data as to exact consumption of air by different tools, &c., because they had been too busy to make experiments, but they knew the system was a good one for their work, and so it was being extended. The erecting shops and some others at Doncaster are piped for air, the pressure at present is 80 lb. to the square inch. Belt-driven compressors of the two-stage type are used, the sma11er sizes have a capacity of about 40 cubic feet, and the larger machines compress about 100 ft. of free air per minute. A detail worth noting is that it is desirable to take the air supply to the com-pressors from as cool a place as possible, and it pays to run a wooden duct leading the supply from a cellar or from the north side of the shop, if colder air can be obtained in that "ay. As regards the difficulty from water in pipes, it is well not to have the reservoirs too near the compressor, but to give the air time to cool, and so leave t he water in the reservoir, and avoid its getting into the supply mains round the shop. The air drills at Doncaster are chiefly of the rotary or '' blow round " type ; those used for tapping st ay holes are provided with a reversing cock. They had four or five different hammers in work one of the chief things to be aimed at was to get a bammer which operates with as litt le vibration as possible. A us~ful application ?f compressed air was also found 1n bor1ng the cyhnders of loco-motives under repair. They had small air engines, with cylinders about 4 in. by 4 in., and pist :>n valves. One of these little engines is cramped to the frame, or " running board " of the locomotive, and belted to tha driving pulley of the cylinder boring or valve-facing machine. These air engines were pro-duced at Doncaster, and consequently they were rather pleased with them. Amongst miscellaneous uses of compressed air was that for whitewashing, already mentioned by. a pre~ious speaker, the plant being fitted up. m ~ ~a1lway truck.. They

h~d tried to clean carriage hnmgs and cushwns by means of compressed air, but not with c?nspicuous success. The apparatus '!as somewh~t hke. a curry comb with an air supply and a flextble dtscharge tube leading from the handl~ to a ~ucket of w~~er outside the carriage. The Jet of a1r cau~~d a~ ~draught at the face of the ''curry comb as 1t IS passed over the surface .of the cloth, ~raw:ing in the dust and discharging 1t by the tail p1pe. The drawback to the arrangement was that it did not do the work fast enough. They also used com-pressed air in place of steam for blowing out the cylinders of locomotive~, and anot~er use for com-pressed air was for tak1ng locomotives out of the shop. They charged the boiler with air from the

E N G I N E E R I N G. (MARCH 30, I 900. -

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mains, blew the whistle, and ran the engine out average saving per rivet was, therefore, 1.69 cents, without steam. making the average cost of machine rivets only

Mr. Harris asked whether Mr. Ivatt used the 47 per cent. of the hand cost; the gain on each shi cooling water in the cylinders of the compressors ordinarily built at the yard was from 6000 dols. t~ as an injection or in a water jacket. Mr. Ivatt 6000 dols. Mr. Babcock stated that Mr. Cram replied that the compressors were fitted with water could hardly expect at the start to be equally sue~ jackets. Mr. Harris, under these circumstances, cessful, but there was no reason why in a compara-considered that there should be no difficulty in tively short time results equally as good should not getting rid of the water in the air. be reached in the Philadelphia yard. "It does

Mr. John Fielding, of Gloucester, said he had not take," he said, "much except ordinary common used compressed air with advantage for drilling and sense and plenty of compressed air to handle these chipping, and had found it better than the Stow machines. " Mr. Marten also read from a docu-fiexible shaft. He considered there was a future ment he had received from Mr. Babcock in for pneumatic riveting under certain conditions, which the cost of compressed air was dealt with and that it would replace a good deal of hand in greater detail. This we also print in full. riveting. It would not, however, supersede hy- Mr. Marliell also pointed out that the arrangement draulic riveting which, in the great majority of of the illustrations in the paper might lead to cases, was much to be preferred, especially for misconception. In the text the data given referred boilers and the heavier class of riveting gene- very largely to one type of hammer, whilst a pro-rally. He was much interested in the various minent position was given to an illustration of a examples of pneumatic hammers described in the hammer of another type; members would do well paper, having himself made one or two pneu- to guard against the mistake of attributing to one ma.tic caulking machines some twenty-five years hammer illustrated the performance of another de-ago. One of these machines which was most sue- scribed. cessfully used in the year 1876 was illustrated by Ch1'cago Shipyards, No. 38.-M'lchine Rivets During a diagram placed on the wall. This tool, it would Three Weeks Ending October 12, 1899. be seen, diff~red in no essential respect from the modern machines. It moreover possessed a feature Distribution. I Number. Size. I M~~~n. e not present in any of the later tools, viz., a spring

Hand Rate.

tool socket by means .of which the weight of blow de-livered could be regulated according to the force with w hi eh the tool was pressed against the work by the hand of the operator. The spring arrangement also tended to reduce the vibration upon the hand. He had not, however, followed up the invention, be-cause he was at the time much occupied with the development of hydraulic machinery, and, more-over, it was then thought by many that with the new system of riveting all necessity for caulking would be done away with. Experience had, how-ever, shown that there was still room for the use of a caulking tool. He believed that the caulking machines he had made were the first of their kind ever employed. He would su~gest that the air pressure for riveting might with advantage be in-creased to 100 lb. per square inch, as in that way the weight and bulk of the machines might be reduced. He would like to hear from those who had used both kinds, whet her the double-stage com-pressor had not, in practice, ad vanta.ges over the single-stage compressor.

Mr. Amos stated at theLondonanclNorth-Western Railway Works they had increased the air pres-sure fr01n 100 lb. to 120 lb.

Mr. B. Martell said the paper was of the greatest interest at the present time. During his 30 years ' connection with Lloyd's Registry of Shipping he had come in contact with a large number of en-gineers, and he could assure the meeting that a great majority of them looked forward to the sub-stitution of this pneumatic machinery for manuit l labour. Engineering employers had great dilli-culties with the labour market; where men could earn enough in three days to keep them for six, there was little control over them, and contractors found great difficulty in insuring the completion of the work undertaken. With this machine they could always depend on six days' labour. It had been his duty for many years to find out whether work, when done, was sound, rather than trouble himself with the manner in which it was carried out. He could say, without hesitation, that the very best kind of work was done with these pneu-matic riveters. In one case, i -in. rivets had been driven and the plates had been slotted through to show how the rivets had been laid- up to fill the holes ; in this respect the work left nothing to be desired. In regard to rapidity of work, he would read from some particulars which had been sent to him from Chicago shipyards, showing t he work done by pneumatic riveters over a period of three weeks. We give in the next column the document referred to by Mr. Mar ten in his speech. The speaker also read a letter received from Mr. W. I. Babcock, the superintendent of the Chi-cago Shipbuilding Company, addressed to Mr. Cramp, Philadelphi~\. This letter was dated last October, and stated that as Messrs. Cramp had made a start on pneumatic riveting, some figure& that the writer had collected would be of interest. I t stated t hat with a total of over 93,000 rivets, the average cost of the machine-driven rivet was 1! cents as against 3.19 cents for hand riveting. This was taking the rates in t hat time in force in the shipbuilding yards of the Great Lakes. The

Keel . . . . . . . . 1 Shell .. .. . . . .

Shell margin (bilge sin~le line) . . .. . . . .

Longitudinals, open . . . . C. V. K. brackets . . . .

, ,

, ' , . . . . . Longitudinal& under tank .. Longitudinal bars . . . . Tank top stiffen era . . . .

, margi n . . . , lugs . . . . . . ., rider . . . . . .

Tank top.. . . . . . 0. V. K. . . . . . . . . Hold stringer . . . . . . Floors . . . . . . .

.. odd . . . . . . C. V. }{. odd . . . . . . Bulkheads . . . . . .

,

,

Total . .

..

6,217 21,1328

1,122 24,63l 3,197 3,197 3,397

664 2,989 1,129 4,033 1,620 3,209 4,467

12,723 1,184

123 5

38 1,318 3,061

231

93,479

lD. 1 i

cents 2~ 1~

cent 4} 3!

4~ 2f 8! S! u

~ 2i 3! 2i 2i 3 3 3 6 6 6 Si 2!

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-

:i

Tota ' cost by machine, 1403.31 dol!.3. ; average, 1 50 cents ea h. Total coat would have been by band 29 6.87 dole. ; average,

3.19 cents eaoh. Saving, 1583.56 dole. ; average, 1.69 cents eaob. Average coat of machine rivet was 47 per oent. or band cost.

CosT oF CoMPRESSED AIB. Compound Two-Stage Air Compressor :

.. . 150 lb.

... 100 lb. to Steam at boiler . . . . . . . .. Air . . . . . . . . . . . . . ..

Revolutions . . . . .. Indicattd horse-power Free air per minute

.. .

Coal, per day of 10 homa . . . . .. Attendance, per day of 10 hours Fireman, per day of 10 hours ... Oil, per day of 10 hours . . . . .. Repairs and maintenance, u1.y ...

105lb. . .. 78 ... 420 . .. 3200 cub. H.

...

...

...

Dols. 11.30 2.00 2.62 0.44 1.00

Total . .. .. . .. . 17.36 Cost per 1000 cubic feet free air com-

press(d ... . .. ... ... ... 0.91 cents. Maintenamoe of P la;nt Outside of CO"mpressor:

Dols. 1.75 2.00 2.60

One lin~ma.n ver day . . . . .. . .. , tool repa.~..rer per day... . . . . .. , lathe band on repairs, dies, and sets , smith on rf'pa.irs, dtes, and sets,

average half da.y . . . .. . .. .

Total Material for repair~,

&c., about lOO dols. per day . . . . ..

Air as above ...

...

replacing hose, per month, say .. . ... .. .

1.38

7.73

4.CO - -

11.73 17.36

- -

Total ... .. . .. . 29.09 This amount of air will run a.b.,ut 30 riveters, 12 reamers,

10 chipping or caulking hammers. In addition, air is supplied to one air hoist in sh?p, and

is used for blowing 30 hea.ti~g forges {one ~or ~oh n vet~), one large rivet forge for sta.t10na.ry st~m nvet~gmaobme, and two blacksmiths' firee. Tbe nveters. will average 400 rivets per day of all claeses, or 12,000 rivets per da~. If the total cost of the air and maintenance of plant IS charged against the riveters, it woul~ a..mounb. to 0.24 cent per rivet. Probably one-half th1s IS a. fall' allow-ance as both reamers and hand hammers are used much mor~ continuously than riveters. . .

In comparing these figures with hand work, 1t JS neces-

~1ARCH JO, rgoo.J := dd also t.> Lhe dirr ot hand cor ~ the Eary of course,l to a he- ..l _, and hd.nd e ~, re pam~ t .>

' f tool" a mmer au...,, . b h th' cost o , ' I nm unable to ~ay JUSt ow muo ts forge11, &J. t but probably 1t wvuld be be~ween on ~would amoun\ 0jr the mn.obine cost. In any event .the third and obe- dded to the direct co3t of th~ ma.ohme-s~ount ~o e a . the corresponding band cost IS less than drtven rlvet ove~nts er 100 rivets. . . 0.10 cent, olr 10 o nt l.nP vested to date in our air plant ts, m The tota amou round numbsrs : Dols.

... Compressor .. " Tools ... ... ... . .. p1pe lines, hos"', &o. ... ... ..

..

Total ... ... ... ..

17.500 28 000 5 000

50.000 duplioatino- our comprf>s3or, which will

We are now aoit but ~11 not h!iVd to add any more dou~l~ropu[p~a.Dne3 ~r anything, except~ perb~p3, a. small too t f hose a.s our outfit of toolg IS far m excess of amoun o '

. ly ouDat~ supfbe' psriod between September 2t and No-};0~ 1899 we drove by air a. total of 335,713 rivets, ~:~di~t cost' or 5649.66 do1~. , average 1.68 cents. The direct co3t C'f the38 rivets by hand woul_d have ~een 10 698 27 dols. , average 3.18 cents. That 1s, . the dtrect M~in of air over band was 47 per cent. Allowm~ 10 c~nts

r 1No for ai r n.nd maintenance woul~ make the a.tr-drL ven ~ets cost 6,985.37 dols., and the ~av!ng over band 44 p:r cent., allowing interest and depra01ah~n or;t plan~ of 16 per

t n addition would make the au-dnven r1vets cst cen 1 t f th t "620 37 dols and (takmg no accoun o e amoun m-~~sted in band plnnt) the saving ove.r hand, 29:1 Jler cent.

It will be observed that as, durmg the per10d under discussion, the plant was ~orke~ only to. abvut one-half it~ capacity, this charge IS tw1~e .what It ~ught to be. When also, the new compressor 1s I~ operation, bo~h the cost of air and maintenance and the 1_ntere~t cost will m~terially decrease per 10~ rivets _dn ven, 1f the plant 1s worked to anything near 1ts. oap~ot~y. .

Finally, i~ is our empba.t1o opmton that If the O?St of air-driven rtvets were equal ~or ev~n somewhat m ex-cess of that of band, the superior qua.hty of the work done, and the far better control we have over our men, would amply jostify our entire outlay. (Signed), W. I . B ABCOCK, Manager,

Chicago Shipbuilding Company. December 12, 1899. Mr. W. W. Ma.rriner said that through the

courtesy of Mr. Yar_row he \yas abl~ to give t~e result of the expenence gamed w1th pneumat1c appliances which are iu use at t.he P oplar yard of Messrs. Ya.rrow and Co. Pneumatic hammers were used for a. variety of purposes such as chip-ping, caulking, and bel! -mo~thing t ubes. V arious types had been tried, but 1t was found that t he "Boyer " was preferred because i t had some special advantages. One was that the shock trans-mitted to the man holding the hammer was so small that there had never been an objection made, in fact, the men much prefer a pneumatic hammer to the hand hammer. Another advantage was thl).t the weight of the blow given by the hammer could be regulated independently of the trigger valve. It was found that the principalvoints needing attent ion too were the hose should be as light as possible, so as to offer the least resistance to the free movement of the tool, and at the s~me t ime it shoulu be of a kind not easily damaged. They preferred good india-rubber hose to metall ic or armoured hoses. All fittings and couplin~s for hoses should be of the same size and t hread throughout the works, and any new tool should be fitted with the standard nipple before being put into use. The tools of pneumatic hammers can be ground much keener than ordinary hand chisels, without much danger of breaking the point, the blows being more uniform than with a hand hammar. Of course the ~een?r tool cuts quicker. In r eferring to pneu-mattc drills, the speaker said that those shown on one of the diagrams (i. e., the Boyer piston drill), were what Messrs. Yarrow generally used, but they had _also several other types. These drills were spectally _useful for drilling holes on the boats in progress m the yard, for drilling a. wk ward pipes that could not be_ got under _an ordinary machine, and also for use 1~ the erectmg shop, where it was not always convement to take the work to a machine. They ha~ also tried this drill for driving s pc cial salf.feedmg expanders for boiler tubes but i t was not fou~d suitablt', as the speed was to~ great and much ttme was lost in getting the expander dut of ~e tub~ after it had done it.q work. The drill had

be dtsconneoted, and t he expander r eversed a ~hn ~Y ha_nd to loo~en it. They therefore fitted e!rdrtll w1th a reducmg gear, and al lOa revers ing r , I SO that the Operator by turning the regu-

thttng valve, could reverse 'the spindle and loosen did expander. At the present time the speaker was ~~t know a more efficient tool for the job. It drill 1~ clll~ague, Mr: ~rush, who saw where the 8

a. e , and ortgmated the idea of making

E N G I N E E R I N G. them slower and r eversible for this c!a s of work. At t he Poplar yard ther e were also in use pneumatic hotsts for hn.ndling ihe work at the heavier machines, and these were found \ ery useful; their only dra wback b eing that until t he operator became used to the regulating valve, t hey wer e rather too q uick in t heir action. At the last meeting, Mr. Wicksteed invited a comparison be-tween portable pneumatic tools and elect rically d riven tools ; and, as Mr. Yarrow had laid down both installations about the same time, th e speaker had had t he opportunity of making this corn pari-son . In the fil'st place, there were, he said, dis-t inct uses for both systems ; for instance, where power is r equired in the form of a blow, com-pn:ssed air is obviously superior, and where it is required to drive a machine above 1 horse-power at some distance from the source of power, t hen electric ity is better ; at t he same time t hor e is a large fi eld in which they would be close rivals.

To make the matter q uite clear, Mr. Marriner considered t he fundam ental differences between the two systems . Firstly, the pneumatic m 11.chines were lighter than electrically driven machines for the same power ; but if a flexible shaft were used in connection with t he elElctric motor, t hen t he d rill press would be much ligh ter, and it would also be much easier to support than th~ drill and pneum

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E N G I N E E RI N G.

THE RIVER RHINE (For De$cription, see Page 408.)

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Ault, having had considerable experience with pneumatic machinery, wished to make a few sug-gestions. First, with regard to wear and tear of the pneumatic tools. He had noticed that com-pressed air contained a good deal of grit and dust, he had held his hand in front of a jet of air and found this grit sharp enough to draw blood from the hand. Naturally, such grit would wear out the working parts, both of the air compressors and of the air-driven machinery. The remedy was to filter the air before compression, which could be readily done by passing it through a wet screen, a wet coke-filter, or by washing it in a scrubber. His second suggestion was with regard to the economy in working t he tools. Complaints had been made of the low efficiency of pneumatic transmission. The reason of t his was that a great part of the work of the air-compressing engine was being converted into heat, and as the air was used cold and non-expansively in the tools, all this heat was lost. "'\\7hen working with an air pressure of 100 lb. per square inch, and exhausting into the atmosphere, it was impossible to get a. higher efficiency than about 28 per cent. from the indicated power in the steam cylinder to the indi~1.ted power in the work ing cylinder of the tool. The loss of power was therefore 72 per cent. This loss, could, however, be materi-ally reduced by working with a closed circuit, using a. return main in the same way as it was used for hydraulic and electric motors. The loss of power due to heating was not dependent upon the working pressure used in the tools, but upon the ratio of compression, that is, the quotient of the higher pressure divided by the lower. Working with air of 100 lb. pressure, and exhausting into the a tmosphere, the quotient is ( ~1: =) over 7, but working with a closed circuit, the lower pres-sure might be kept at 100 lb. per sq uare inch, and the upper pressure at 200 lb. This would still give an effective working ratio of corn pres-sion instead of being over 7 would be reduced

t o ( 215 = ) less than 2. He, therefore, recom-115

mended that the air compressor should draw air from a. low-pressure air receiver, where the pressure was 100 lb. per square inch, and discharge it in to a highpressure air receiver at 200 lb. per square inch , and that the pneumatic tools should draw their air supply from t he high-pressure air receiver and exhaust into the low-pressure air receiver through a. return main. The compressed air would thus be used over and over again. This system had been used successfnlly in some American mines, but did not appear to be generally known. It involved some additional complication in the mains, but working in the manner described it was possible to raise the efficiency from 28 to 53 per cent., and the working expenses could thus be re-duced nearly to one-half without making any altera-tions in the tools themselves. He thought that this matter was well worth the consideration of t hose who intended to introduce pneumatic tools into their workshops.

~Ir. Samuelson, in replying to the discussion, said he wished it to be understood he did not infer that power hammers would take the place of stea'!l hammers for all purposes. From present experi-ence he would not care to undertake to build a power hammer over 10 ~wt. He was not ~ure th~t he quite grasped the 1mport to Mr. S1mp13on s question. In the paper the steam and power hammers had Leen compared at full stroke and utmost capacity, as that appeared to be the fairest method. His old friend , Mr. Chambers, who spoke at the previous meeting, had been so mew hat inac-curate in his statement; he, the speaker, had found that the first hammer had been down for seven years and uot five year.s, as stated . He had never been in a position, unttl recently, to know., what was the nature of the work being done by Mr. Oha.mbere. Mr. Chambers determined to do everything for hi~self and kept it all secret, and took all respo~slt>ili ty of design. Ho had overtasked the machme which, he bad said, had been returned as a wreck, but this hammer, as a matter of fact, after a fe.w repairs, was disposed of as a second- ban~ tool1n 1896, and had been put to work aga,m u p~n 10 hour's daily and continuous work, and was still running. Th~y found subseq uently that the work done by Mr. Chamben; was l"leing stamped on both s ides of the tupp, as well as und.er the centre, tl~us setting up severe alternate strams and a?countmg for the deterioratio:1. In rrgard to the adJ US'ments

E N G I N E E R I N G. for which Mr. Chambers asked, all had been given him except the one which had only been stated to be found necessary by Mr. Chambers after an inten~al of eight years. Mr. Boorman had said that a single blow could not be given. He thanked Mr. Chambers for having denied this, and he himself wished most emphatically to state that a single blow could be struck almost as easily with a Longworth hammer as with the steam hammer, after the . operator had obtained a very little prac-tice. He had not considered the problem of using compressed air in a s team hammer.

Mr. Amos said that he was not responsible for the arrangement of illustrations in the paper. If more attention had been given to one hammer than another, it was because one had only just been s tarted in this country, whilst of the other there was considerable experience. The pressure of air required varied according to the class of work to be done. For s triking a blow and riveting the pressure should be higher than for drilling, unless, with the latter, for very heavy work. In the mains the pressure should start at lOO lb. to 120 lb., and t here should be an easy means of reducing pres-sure.

In bringing the meeting to a close, Mr. Wick-steed said that the next meeting would be on April 26, when Professor Hele-Shaw would read a paper on "Self -Propelled Carriages, , Mr. Donkin having kindly withdrawn his paper on " The Condensation in Steam Engine Cylindera , for the present to suit the arrangements of the meeting.

ARCIIED BRIDGES OVER THE RHINE.*

[MARCH 30, I goo. 12 k~logrammes per square centimetre. Thecal-culatwns for the bearing capacity of the super-structure .h~ve beon based upon the most unfavour ab.le co~d1bons ?f. dead and moving loads that might anse, smgly or JOintly. The maximum load for the footpaths crowded with people has been estimated at 500 kilogrammes per square metre for the whole bridge at 400 kilogrammes per squ~re metre. As regards the roadway, steam and electric trams a 13-ton steam roller, and cart.q have been taken U:to consideration, and the moving loads are reckoned equivalent to 1.3 of the dead loads. The wind pressure has been allowed for at 150 kilogrammes per sq uare metre (31 lb. per square foot) of actual surface when under load, including a belt rising 2. 5 metres (8 ft. 3 in.) above the road-way, and a.t 250 kilogrammes for the wind area not under load. The temperature fluctuations may have a range of 60 deg. Cent., between - 20 deg. and + 40 deg. (- 4 de g. and + 104 deg. Fahr. ). The calculations proved that the most unfavourable condit ions would occur, when the trackway and the one footpath be loaded to their fullest capacity, while the other footpath remains empty. The graphic statics of Muller-Breslau limit under these circumstances the stresses per sectional unit, owing t o vertical dead and live loads, to

k=950 (1+ ~min. 8 ) max. S

in kilogrammes per square centimette, where S indicates the absolutely lowest or highest strajn. The maximum permissive stress for vertical load, wind pressure, and temperature variation is 1425 kilogrammes per square centimetre (9.05 tons per square inch). F or parts exposed to wind stresses

(Continued from page 349.) only, the limit is 700 kilogrammes per square centi-WE come now to the superstructure. The metre (4.4 tons per square inch). For rods under

different competitors had proposed arch, suspension , compression, a factor of safety of fire, according to h Euler's formula, has been demanded as a minimum.

and girder bridges. A girder bridge, it was thoug t, Mild steel, mostly from basic Siemens-Martin fur-would require considerably more material and d hardly please the public taste. Suspension bridges naces, has exclusi\'ely been used. Two hundre sets

h of samples were tested, and six of these rejec~d. need high piers, and do not convey t e impression The breaking tests yielded as averages, longitudinally of the solid strength of the arch . Preference was, ~9. 8 kilogrammes per square millimetre (25.3 tons therefore, given to the arch. To arrange the 6 6 road way tangential to the crown of the arch was per square inch), with an elongation of 2 . per cent. out of the question, considering the fiat banks of (the stipulated limits were 37 to 44 kilogrammes, the Rhine, which enters the lowlands at Bonn, and 20 per cent. ); and transversely, 40.11 kilo-

grammes (25.4 tons per square inch), with an and the clear waterway required for shipping. The elongation of 23.85 per cent (limits specified, 36 and case is different at Niagara Falls, at Mtingsten, and 45 kilogrammes and 17 per cent.). . . \v ith the I{ornhaus Bridge at Berne, to q uote a few The members of the girders are fix ed m vertical recent examples of fine arched bridges, where steep ) Th f 11 bluffs rise from the river . This applies also to the planes, 9 metres (29 ft. 6 m. apar~. e . u

width of the road way and footways combmed Levensau Bridge over t he North-East Sea Canal, ) h f t which, as we pointed out in a previous article, was being 14 metres (45 ft. 11 in. , t e oo wa~s

project by 2. 5 metres (8 ft. 3 in.). The span IS built by the same firms, the Gute Hoffnungshutte 187.92 metres; the rise of the lower boom 1s 29.6 and R. Schneider, of B~rlin . It was decided at metres. The distance between the two members Bonn to place the roadway underne.'\th the arch, in the same vertical plane decreases from 10.6~7 so far as this is possible ; as we shall see, only to 4. 8 metres (about 34.5 ft. and 15.8 ft. ). The pm the first two panels are intersected by the road way. of the bearing lies at + 9.52 metres B.P.; the An intermediate solution was also thought of, the arch culminates at 45.5 B.P., 42.75 metres one adopted at the Grunenthal Bridge over the (141 ft.) above mean water level. The arches N orth-Ea.st Sea Canal. In the Gri.inenthal cutting are divided into panels of uniform length, 7.8 the rail track crosses the crescent-shaped girders at metres (25 ft 7 in.), and the panels are num~ered about mid height. Our readers may compare the 1, 2_ 12 from the piers to the middle of the brtdge. Levensau and the Griinenthal Bridges in our issue In most of the diagrams the ,erticals are nu~bered, of August 16, 1895. Personally, we share the beginning with vertical 0 next to the p1er (see liking for the graceful crescent-shaped arch which Fig. 43 on our twopage plate). seemed to predominate on the canal. But we The arched ribs are box girders, but only the upper readily acknowledge that the bowstring girder arch members are covered in throughout ; the lower appears better adapted to t he local conditions on members are mostly open on top and bottom. I!l the Rhine, and that the Gute Hoffnungshutte has Fig. 45, at the bottom of our twopage pl.ate, maXI-erected a handsome, harmonious structure. f th ders are mum and minimum sectwos o e gn

The road way is suspended from the main arch and grouped together, three of the upper members borne by the side arches, which, indeed, appear as being marked U, those of the lower L. ; the V refers continuat ions of the lower members of the main h d 1 The to the verticals the D to t e 1agona s. girder . The rise of the main arch- of which we smallest section; of the main arch ribs are for~ed shall speak now-is such that at full load the re- by webs 680 by 8 millimetres (26.8 in. by 0.3 m.), sultant of the t hrust on t he piers would cut the 544 millimetres apart, with fou.r angles of. 14~ axis of tho pier base. The maximum pressure of by 140 by 15 millimetres (5.5 m. by 0.~ m.), the iron structure against the Rkewbacks is 50 the efficient area is 269 square cent1metr~s kilogrclmmes per square centimetre (711 lb. per (41. 7 square inches). The central panels conta1~ square inch). This maximum pressure could arise the weakest lower members, two webs, 7~~ by 1 in two ca.ses; during the construction, because the millimetres (:30. 7 in. by 0.47 in. ), 538 m1lhmetillr~s main arch was erected before t he side arches ; and (21. 2 in.) apart, four angles 160 by 160 by 19 m 1: afterwards, with fully loaded side arch and un- metres (6.3 in. by 0. 75 in.), and four ~aoge plates 4 loaded main arch . 'rhe maximum pressure on t he the efficient area is 506 square cent1metres (78. subsoil, corresponding to these cases, would be square inches). The webs of the upper boom~ 5.2 or 5. 6 kilogrammes per square centimetre. By were all rolled in full width, those of t.h~ loweer erecting the main arch without the footpath in members in two paTts, 525 and 255 mtlbmetr the first instance, the figure 5.6 has been reduced (20. 7 in . and lOin. ) in height. The segments are not to 4. :~. The strcsse::; in the stone pier do not exceed ~tr~ight, but curved to circular arcs. The w~bs --

* The pr~v ions articl~s F~bru:l.ry !) and ~!arch 16.

appea.rt_d_ i_n_ o_u_r - i-s~-UlS ~ had, tlurefore, Lo pass t~uough a special pla~dlD~ machine, in which the hon zontal plates were gut e

fvlARCH 30, I 900. J E N G I N E E R I N G. -- . cular path and cut simultaneously by two them plates, of 310 by 10 millimetres. The gal-~~~rs c~ both edges. The gradual streng~hening vanised 6-millimetre (0. 2 in.) buckle plates (Fig. 50) of the rib sections u~ to 9~9 square centimetres are fixed to these last-mentioned flange plates. (1 ... 5 are inches) ruaxm1um m the case of the upper The general arrangement of the road way will be 0 ~:rs and to 1630 square centimetres (253 understood front Figs. 43 and 44; details of the con-

~~:re in'ches) in the case of the lower ~el!lbers, nections between the rods and the transverse ,!s effected by weans of one or two 15-nulhmetre girders can be seen in Fig. 52, page 406; Figs. 49, 0_6 in.) plates on. the w~bs, and up to t~re.e 60, and 51, on our two-page plate, show con-l9-millimetre (0. 75 m.) flat uonE', or two 10-milh- structi ve details of the girders. Vve notice in the metie (0.4 in.) flange plt~otes. The lower angles of webs, apertures for the gas pipes, which are the two halves of the upper members, and the upper spirally welded, and for the drain pipes. The

d the lower angles of the lower members, are hrackets are built up of two [ -irons with an inter-afffi ed by means of lattice bars, as well as by the mediate web as upper boom, and two angle and a 8 1 t~~ls which are riveted into the girders and the plate of 105 by 12 millimetres as lower boom. ~~r ~ragms of the wind bracing. Figs. 46 and 47 Of the longitudinal girders, five run und erneath ~a~ oints in the booms. The diagonals D of Fig. 43 the roadway proper, and two under each footpath. s

0 sJt of two or four plates from 340 to 400 milli- rhe extreme footpath girder is 0. 65 metre (25. 6 in.)

contres (13.4 in. to 15.8 in.) wide, and from ~2 to from the outer edge. The five are at equal in-~eo millimetres thick, joined to both the Inner ter,als apart (Fig. 44); three of them are 1-beams, su~faces of the webs, and of t'Yo angle:irons 10~ by 750 o: 6~~ millimetr~s (29.5 or 2~.6 in.) h~gh, best 100 by 12 or 14 millimetres ( 4 m. by 4In. by t 1n. ). seen 1n FIg. 53 ; the two outer gtrders, still under 0 osite angles are connected by lattice stays.; the ~oadway proper, a:e connected with the. wind tt!sections of these diagonals vary betwec~ 16.3 : bracUJg, a~d are lathc~d: The footJ?ath grrders and 301 square centimetres (25.3 an~ 46.7 s~ .. In. ). have. a ~e1gh~ of 500 millimetres (20 I_n. ). These

Close to the pier the road way Is, as l.i 1g. 43 long1tudmal girders are not to act as tie~, and are

--

shows, supported by the v~rticals matked V . in Fig. 45. Apart from the vertical No. 2, down whiCh the wind bracing is carried, they are all !-beams, 500 millimetres (20 in.) in height, with four angles. Their efficient eection increases from 261 to 348 square centimetres ( 40 to 54 square inches); they fit exactly into the ribs; in the weaker panels only, intermediate plates have been inserted. The suspension rods are joined to the third and the subsequent verticals, and consist of webs 476 by 8 millimetres (18.4 in. by 0. 3 in.), and four angles 100 by 100 by 10 millimetres. These rods have to bear the direct load which may amount to 75 tons and, further, to absorb the longitudinal temperature distortions. Rods 4, 5, and 6 have, therefore, a web thickness of 12 millimetres ; while the angles have been reduced to 80 by 80 by 10 millimetres. The latter two rods have lengths of 8.5 and 11 metres (28 ft. and 36 ft.) ; rod 4 is only 5. 5 metres (18 ft.) long. At this last point a further strengthening was required, and a kind of elastic band joint has been adopted, the feur angles being replaced by fishplates : two in the upper part coverin.g a length of ;6 in. ; two in the lower part: extending over 24 m. Further details of the arched ribs and verticals can be seen in Figs. 48, 49, and 59, the two former on our two-page plate and the latter on page 407.

Corresponding to the panels of the arched ribs the roadway is divided into sections 7.8 metres i~ length. The suspension rods are connected with transverse girders which are produced to form t~e lattice. brackets of the footpaths. The cross ~~ders_ (Ftg. 49) are deepest-1210 millimetres h4~.6 m.)-about the longitudinal axis of the ndge, over a length of 3.6 metres the depth :r~es to 1~10 millimetres (39. 7 i~. ). At the 121~bum sect_10~, the girder consists of a web 12 . ~ 12 millimetres, angles of 100 by 100 by 100 ~m~etres, two lower flange plates 260 by ~ 1 tmetres, and two upper flange plates the pP ates 210 by 11.6 millimetres, and under~ea.th

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hence cut at vertical No. 3, as will be explained presently. The roadway is further supported at equal intervals of 1.56 metres (61 in.) by cross I-beams, four of which belong to each section of 7.8 metres length. To these beams correspond smaller-sized beams under the footpaths ; they are secured to the girder next to the gutter, and rest upon the extreme girder near the parapet. The concave buckle plates of the roadway are 110 millimetres ( 4. 3 in.) in depth ; they are covered with beton, the l~yer varying in depth between 75 and 190 millimetres (3 in. to 7. 5 in.), and levelled above with 20 millimetres (0. 8 in. ) of cement. The tram rails are en1bedded in cement mortar. Of the wooden pavement of Swedish pine, longitudinal rows were first laid along the rails ; then came the other blocks which are separated by cross joints 0.4 in. in width, filled with cement mortar. The two rows of blocks along the gutters are lower and cast with asphalte cement. Plane plates reach over from the edge girders of the road-way to the inner girder of the footpath (Fig. 53, page 406). The kerbstones of basalt lava are fixed on these plates by means of riveted brackets and angles. Behind the kerbstone, conduits have been provided for water pipes ; the conduit on the down-river side contains for the present only a cable by means of which further pipes or cables may be drawn in. The footpath is paved with 40-milli-metre (1.6 in. ) slabs of beton, 0.6 metre (2ft.) in length laid between the fl-irons ; over these comes a. layer of rammed-down beton, 2 in. in thickness, and finally 0.8 in. of aspha.lte.

Both the girders and the roadway are provided with wind bracings. The main wind bracing begins at the bearings of the arch, follows the lower membero up to vertical 2, ascends in this vertical which has been developed into a strong portal (Figs. 54 to 58, page 406 and present page), and then proceeds along the upper metnbers. The right and left halves are symmetrical. In addi-tion to strengthening the main ribs for this pur-

:

pose, there have been put i.n the plane of the upper members at each vert!cal, .cross-stays, c~nsisting of 400-millimetre latt1ce guders, each with two angles, 100 by 70 by 8 millimetres, al?d further double diagonals. The la:tter _are ~mlt up each of four angles varying m d1mens1?n.s between 14.0 by 140 by 16 and 65 by 65 by 8 milli-metres at their intersection the angles are 350 millim~tres (13.8 in.) apart, and they taper towards both ends The horizontal sides of these skeleton boxes are latticed with flat irons, 50 by 8 milli-metres, the vert ical sides with angle irons, 60 b.y 80 by 8 millimetres. Very good photog~ap_hs of thlB wjnd bracing will be found in the descnptwn_of the Dusseldorf Bridge, which will follow th1s art10le on tho Bonn Bridge. The photograph of the po~tal re-produced in Fig. 54, page 406, gives a clear Idea. of the general a.rrangemenb. We also see that w1th vertical 3 a lattice-girder bracing is introduced be-tween corresponding poi~t s of the lower girdc~s, as well as a system of diagonals, formed of angle u ons of 70 by 70 by 9 millimetres, placed in the plane of the verticals (Fig. 49), which transfer the stresses over to the upper booms. The same stiffening is re-peat ed between the lower booms and the roadway.

Fig. 58.

As already pointed out above, the wind bracing of the roadway (Fig. 53, page 406) is joinfd to the edge girders of the roadway proper. Flat plates riveted to the girders reach over to the inner longi-tudinal girders of the footway. These plates and the buckle plates make the upper bracing. The lower bracing comprises webs of 400 by 12 millimetres, with two angles of 110 by 110 by 12 millimetres connected with the lower booms of the longitudinal edge girders ; further, there are the transverse girders and a double system of diagonal stays. The arrangements resemble those just described for the arched girders, but smaller sections have been adopted. The bracing would have afforded suffi-cient strength. In order to meet all lateral vibra-tions, however, the extreme longitudinal girders under the footway have, by a reticu]ar system of stays, been joined with the buckle-plate girders, special calculations having proved that the extreme longitudinal girders would not be unduly exposed to stresses by this connection.

The longitudinal girders and the roadway wind bracing could not be made continuous lest the roadway should participate in the stresses of the arch. The cut is at vertical 3, as shown in Fig. 55 above and Fig. 57 on page 406, and 1nore in detail in Figs. 63 and 64 on our two-page plate. Brackets riveted to the transverse girder of the roadway at that point form a bearing, on which the edge longitudinal girders rest with their upper booms, and the three inner longitu .. dinal guders with their lower booms. Castings

410 E N G I N E E R I N G. [MARCH 30, I 900.

12-POUNDER QUICK-FIRING FIELD GUN AND CARRIAGE. CON TRUCTED BY :.ME ' ' R~. VICKER ', SON ' , AND :MAXIM, LIMITED, AT THEIR ERITH WORK~, KENT.

(For Description, see Page 412.)

Fig. 51. Soale j tA

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MARCH 30, I 900] E N G I N E E RI N G.

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12-POUNDER QUICK-FIRING FIELD GUN AND CARRIAGE. CON TRUCTED 13Y l\IE RS. VICKEH. ', 'ON. ', AND l\lAXlM, LIMITED, AT THEIR ERITH \VORK., KENT.

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(For Dcsc1iption, see Page 412. )

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Fig.54.

F rcs. 53 r o 55. BREECH M ECH ANI SM .

F IG. 56. LIMBER AND \VAOON.

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fixed to the transverse girder on the one side I plate, has t wo sliding bearings on the pier, also a ' clearing may vary by 30 millimetres, lt in. in all. r~d t~ the lower booms on the other, preven t any guide block, sliding in a trough in the pier, and, The joint is covered by 13-millimetre (0.5-in. ) plates a era sway. That. part of t.he roadway is thus further, near the bearings, double anchors, which, of corrugated iron which are fixed to an iron of ~upp.orte.d by th? pter, wpere it has free~om of whilst allowing. oscill~tions, tak.e up any tilting [ .section, serving as kerb for the wooden pave-ongttud.mal mot10n, and by the suspension rod moment. that mtght anse from d1fferences of level. ment near the pier (Fig. 66). Corresponding to ~ vertt~l 3, whi~e it is fixed in the por tal. \Vith the extreme temperature deviations of 30 deg. this [ -beam is a Z -girder, bolted to the p ier ; tra~ de~ F?ross grrder of the roadway, illus- Cent . (54 deg. Fahr.) from t he mean temperature the upper edge of t his girder lies 1.25 in. below

e m Igs. 66, 66, and 67 on our two-page of 10 deg. Cent. (50 deg. Fahr. ), the width of the 1 the [ -beam. Small gutters lead away any water

412

dripping throu~h the gap. On the footpaths, which are earned round the towers of the piers,

t~e cut st arts from the bracket joined to the ver-tiCal 0, and proceeds obliquely out ward, as is

marke~ in Fig. 44. The [ irons and corrugated ex~answn cover-plat es are of the kind just de-scrl bed, and similar provision has been made on the other side of the pier where th e side arch b egins. The .end c~oss girder an~ the expansion plates are pr?vided w1th grooves ( F1g. 65) for the rails. The ratls themselves ~re provided wit h expansion joints, long fishplates w1th oval bolt-holes, which leave the b olts some longitudinal play. A similar adjust-

me~t ha.~ been provided for the extreme longi-tudinal girders under the footway. The level dif-ferences between the tw0 parts of the road way c~used by the elo~gation and temperature cxpa.n~ swn of the v~r~lCals and suspension -rods, n1ay amount to 12 m1lhmetres (0.47 in. ). To counteract t hese effects, t he bolt connections, three in each case, between t he end cross girders, the upper booms of the longit udinal girder, and the vert icals of ~he lower latticed wind bracing, have been allowed a h t tle play. The longitudinal variations in the open join t at vertical 3 may reach 20 millimet res (0. 8 in.) in eit her direction. The adjustment has b een effected in practically the same manner as n ear the stone pier, but oak balks have bet!n substi-tuted for the sp ecial girders spoken of.

The arch rests with t wo pin bearings on each pier (Fig. 43). The bearing block (Figs. 60, 61, and 62), is a ribbed piece of cast iron 2.2 by 1.8 metres (86.6 in. by 71 in.) on its lower, and 1.2 by 1.25 metre (47 in. by 49 in.) on its upper base, 0.8 metre (31.5 in .) high, weighing oYer 10 tons . It leans against the ske wbacks of granite, which are care-fully coated with cement mortar, and are entirely embedded in bricks. A piece of sh eet lead, 4 milli-metres (k in. ) in t hickness, forms a cushion for the iron block, which in its turn holds the saddle bear -ing ; the latter is secured by means of four lateral steel wedges and by as many underneath. Tempo-rary wedges were inserted during the erection of the arch. The arch ends in a semi-cylindrical shoe which corresponds to the bearing shoe of the saddle. The flanged p in, lying on these shoes, has a length of 925 millimetres (36. 4 in. ), and a diameter of 250 millimetres (10 in. ). All these parts are in steel. The largest gran tte blocks of the skewback are 1.195 by 2.4 by 0.7 metres (47 in. by 94.5 in. by 27.6 in.). U nderneath are blocks of basalt Java.

(To be continued.)

MODERN FIELD ARTILLERY. (Continued from page 373.)

THE 12-P ouNDER GUN AND ITS E QUIPMENT. MESSRS. V IOKERS, SoNs, AND M AXI M manufac-

ture several types of 12-pounder breech loading quick-firing guns, including a naval gun with a muzzle energy of 632 foot-tons, usually fitted on a conical mount; a field gun ; and a separate gun, t he latter made t o be detachable in parts along with the carriage, so that men may carry it in sections with its equipment. This latter gun we shall illustrate in our n ext art icle ; in this issue we illustrate the equipment of the field gun, a general view of the carriage being shown in Figs. 51 and 52, page 410, while the engraving, Fig. 50, shows the carriage limbered up.

The gun itself is of steel and of wire construc-t ion; it is 22 calibres long in the b ore, the total length from the breech face to the muzzle being 5 ft. 11.05 in. It is constructed with a strong inner tube, round which wire is t ightly wound, th e wire extending over the chamber and that port ion of the bore where the highest pressures are exp erienced. The wire is covered by a s teel j acket, which ex-t ends the whole length of the gun, and is connected by shoulders t o the inner tube at the chase and muzzle. At the breech end a bush is screwed into the jacket holdin~ the inner tube in .posit ion. The bush is screwed Internally to receive the breech plug of th e mechanism. . On t he ja:cket there a: e formed t runnions by wluch the gun 1s supported 1n the carriage, and there are bosses for taking t he sigh ts.

The BrePch lt!echrcnis1n (F igs. 53 to 55, page 411). - The breech mechan ism is opened or closed by the h orizon tal movement of the hand-lever, so that t he same action rotates, locks or unlocks t he breech plug, and swings it around the pivo.t on whic~ it is mounted . The arrangemen t consists of a hnk, one end of which is pivot ed on a pin projecting from the r ear face of the breech p lug, so that the

E N G I N E E R l N G. link works in a plane parallel to the breech face of the gun. The other end of the link is pivoted to a short crank, which is mounted on the plug carrier, and around the b oss of this crank are formed sk ew gear teeth. The hand-lever ior actuating the breech mechanism is pi voted on the plug carrier, and moves in a plane at right angles to the breech face of the gun. Around the boss of this hand-lever is fitted a skew gear wheel which gears with the sk ew gear t eeth formed on the boss of the crank.

The whole is arranged and proport ioned in such a manner t hat when the breech is closed, the hand-lever lies close up to the breech face of the gun ; the centres of t he link and crank are so arranged that when the breech is closed the centre lines of the link and crank form a nearly straight line, the pivot joint at the link and crank being a lit tle past the dead line cent re, thus forming a locking point. This arrangement of centres and pivots, together with the relative lengths of the link and crank, pro-vide great power when opening or closing the breech. On swinging the hand-lever away from the gun when opening the breech, the crank moves the link past the locking cent re a short distance without causing any perceptible movemen t of the plug. The further movement of the hand-lever causes t he crank to turn, and by means of the link rotates the plug, at first very slowly (thus obtain-ing great power), and t hen more rapidly until it becomes unscrewed . The carrier then moves with the lever swinging the plug clear of the gun.

The firing gear is arranged for firing with friction tu be, and is operated by the link of the mechanism, so that at the fi rst movement t o unlock t he breech plug it becomes impossible to fire the gun. An extractor is fi t ted t o this firin g gear, which auto-matically ejects the empty tubes during t he open-ing of the breech mechanism. A retaining ca tch automat ically worked in connection with t he ex-tractor prevents the t ube from being jerked out when closing the breech.

The breech plug is of special construction, and is threaded in segmental por t ions in st eps of varying radii. By this arrangement, the plug, which is divided into six segments, has two-thirds of its cir-cumference threaded and useful for meeting the st rains on the breech, while the ordinary breech plug has only half its circumference threaded, and similarly useful. This enables the breech plug to be very short, so that it can be swung clear of the breech after unlocking, without any curvature, and without the usual longitudinal withdrawal of the plug.

The Field Carriage (Figs. 50 to 52). - The car-riage, which is illustrated on page 410, is prin-cipally constructed of steel, and consists of a top carriage with elevating and t raining gear, trail r ecoil buffer, axle, and wheels. The top carriage is pivoted at its rear to a bracket contained on the t rail, and at its front end is clipped to another bracket on w hi eh it is free to move so as to give

Particulars of 12-Pounder B1ecchloading F ield Gun. Weight of projecbile ... Diameter of bore Length of bore ...

...

.. .

.. . ...

... ...

Total length of gun . . . . . . . .. Diameter of chamber .. . .. . . .. Lenp;th of chamber . . . . . . . .. Ma.x1mum pressure in chamber ... Weight of charge .. . . . . . .. Total weight of gun and mechanism Muz:de velocity . . . . . . . .. Rounds per m mute ... . .. .. . Length of recoil . . . . . . .. Diameter of wheels ... ... ... Track of wheels .. . . .. . .. Angle of elevation . . . . . . . ..

, , depression .. . .. . .. . , training . .. .. . .. .

H eight of axis of gun . .. . . . . ..

Weight of carriB~ge ... ... .. .

12.5 lb. 3 in.

22 calibres (66 in. )

71.05 in. 3.4 ,, 9. 66 ,

14.5 tons 13,75 oz.

605 lb. 1560 foot-sec.

12 30 in. 60 , 62 ,

16 deg. 5 ,, 8 ,. 44.75

cwt. qrs. lb. 12 3 20

, limber, including stores and 40 rounds of ammunition ... 14 1 22

Weight of wagon with storei and 60 rounds of ammunition ... ... 17 3 19

4 deg. training on either s ide of the centre line ; it is provided with bearings and cap-squn.res for taking the t runnions of the gun.

The elevating gear is contained in th e top car-riage, and consists of a handwheel with a spindle actuating a pair of bevel wheels, one of which is formed as a n ut in which the elevating screw works ; this screw is conn ected to a lever hinged to t he top carriage, and on this the gun rests. The training gear is placed on t he left-hand side

,

[MARCH 30, I 900. of the trail and consists of t wo bevel wheels and a s?rew working in a nut connected to the top car-riage.

'l'he trail, which is constructed with steel plates strengthen ed by transoms, is fi t ted with a sho~ provided ~ith an eye for limbering up. In front of the tra1l and on the other side is a bracket for a ttaching the piston of the recoil buffer. The axle is secured to the trail by brackets.

The axle is stiffened by means of a steel plate fi t ting over it , and on this plate are fastened, as shown in Fig. 52, two ammunition boxes, which are each fitted to hold t wo shells, two cartridges, and two fuses ; the shells may be carried fused if re-quired.

The recoil buffer consists of the piston, hydraulic cylinder and spring (Fig. 51). The hydraulic cylinder, which is connected to the trail by chains, is fitted with a strong spade at t he rear. All parts of the carriage are free to recoil except the recoil buffer.

On firing, the spade is forced into the ground, thereby arresting all movement of the cylinder r earwards, but the trail being free to move to the rear, forces the piston-rod into the hydraulic cylin-der, thereby displacing the liquid, and at the same time compressing the spring. After the energy of r ecoil has been absorbed, the part stored up in the spring serves to run t he gun forward into firing position again. If required, the recoil buffer can be removed and the mounting used as an ordinary fi eld carriage.

The carriage is fitted with a travelling brake, which can be manipulated both from the rear and front of the carriage. The brake is housed against the sides of the trail during firing. A handspike made of steel t ube is provided for moving the trail, and is housed on t he trail in two bracket~.

TheLirnber (Figs. 56 to 58, page 414).-The limber, of which various views are given, is constructed to carry 40 rounds of amm unit ion, and consists of the axletree, framework, limber, box wheels, and pole. The axle is built up, and consists of a thin steel tube around and along which are fitted two girder-plates, with their flanges riveted together, and the diverging top flanges riveted to the steel angles forming the frame of the limber. To this frame work ar& fixed the axle-arms, which are finished to receive the same pattern wheels as u~ed in the c~r riage. The drag-hooks, the extenswns of whiCh serve as stays for strengthening the framework, ar fixed to the front angle of the frame ; to this is also attached the fitting for the pole. The footboard consists of a perforated steel plate riveted on lo the frame. To the r ear end of the frame is fixed the limber hook, which has a projecting plate for the buffer spade to rest upon when travelling.

The limber box is composed of a skel.eton frame covered wit h t hin steel plates. In .t~lS skel~ton box are, housed in guides, the ammumt10n ~arners, which serve as stores and portable mag~zmes for transferring the ammunition from the hmber . to the gun. The pole is made of steel tube w1th necessary fittings for at taching the same to the limber. . .

Wagon (Figs. 56 and 59).- The am~u.rutio? wagon, which carries 60 rounds of ammu~1t10n, lB constructed on the same principle as the hmb~r as regards axle, frame, and box. It is fitte~ w1t~ a short t rail pole, provided with an eye for limbe~ng up. It is also fi t ted with a travelling brake, wh1ch is actuated from the r ear of the wagon. .

Amnvnnition Oar1iers.-The ammunition earners are made of aluminium alloy, and provided with a leather handle for carrying ; they are arr~nged internally to hold three shells, three cartridge~, and t hree fuses, and are fitted with a. loose ~artl tion, which separates the shells from the cartrtdg~ and fuses. This partition is so arra~ged tha~ 1t can easily be r eversed, and by so domg suffiCI~nt room is obtained to enable the shells to be earned fused. (To be continued. )

TH E LANGEN !t'IONOR .

MARCH 30, 1900.] E N G I N E E R I N G.

=. part of which was in working order all last rtver, er and which will be opened to public traffic ~~~:a c~urse of this year. Tl~e system. is that of E Lnn

E N G I N E E R I N G. [~1 ARCII 30, I 900. mechanical vibrations of the drum. On to the drum was

att~ched one carbon of a microphone, and the induced osc1llations were thereby considerably magnified in the microphone circuit. This circuit was also arranged in the same way as the former, and by means of another microphone the vibrations were transferred to another circuit, where their intensity was sufficien t to actuate the diaphragm of an ordinary telephone receiver to such an extent as to render the sound pArfectly audible.

LIMBER A

~Ir. \Yatson described some experiments which he had shown to illustrate syntony, both by obtainina- galvano-meter dafiections and sparks in the secondary Circuit.

Dr. L ehfeldb asked bow the circuit was tuned when it ~ontait;ted both a variable capacity and a. variable self-lnductlOn.

~I~. Sha_w said tbab the valu~ of the ca.pac.ity and self-mduct10n were connected w1th the vibrat10n fre-q uency by a. formula given by Dr. L odge. Starting with a known capacity, the necessary self-induction was cal-C?ula.ted and small alterations produced by means of an u on core.

:Mr. Shaw then read a paper on "An Electrical ~licrometer." In this paper the motion of the centre of a tele-phone diaphragm was meas ured by means of a system of l~vera and a s~herometer screw. 'be screw, which had a. p1tch of 0.5 millimetre, and a head divided into 500 parts, pressed against the long arm of a.n aluminium lever. The short arm of this lever pressed against the long arm of another, and so on through three levers. In this way any motion of the spherometer screw was transmitted to a fine pla.tino-iridium point close to a small pla.tino-iridium disc fastened to the centre of the telephone diaphragm. Since the hea(l of the spherometer could be accurately read to 0.1 of a division by means of a. t ele-scope, and since the system of levers minified any motion a hundredfold, it follows that an accurately observable twist of the spherometer bead corresponds to a movement of a millionth of a millimetre, or 1 1.1. p. of the fine point. To test the action of the levers, the point was removed, and a. convex lens was substituted. This lens formed one of a system by means of which Newton's rings were pr0-duced and observed. By means of an optical experiment the author has found that 0.1 of a division on the graduated bead equals 1.033 p. J.1. at the platino-iridium point. The point and the diaphragm th~n formed part of a circuit containing an ordinary telephone, and the levers were so adjusted that the point just touched the diaphca.gm. A sharp check was then heard in the tele-phone. A small current was then sent through the electromagnets of the original telephone, and the dis-placement of the diaphragm was measured by turning the spherometer screw until the point just touched it, and a second click was heard. By carrying out a series of ex-perimf:nts of this description, a curve has been dra.wn, showing the relation between current strength and diaphragm displacement. It is then interesting by exter-polation from the curve to find the movement which corresponds to the least audible sound. The author has done this, and finds that he cannot hear sounds if the amplitude is less than 0.37 J.I.JJ., A motion of 50 P.JJ. gives comfortable sounde, 1000 J.1. JJ. uncomfortable sounds, and 5000 J.l. J.I.SOunds unbearably loud. Throughout the experi-ments it was necessary to get rid of extraneous vibration by means of india-rubber balls and door-spring suapen-SlOns, and by working at night.

Professor Everetb expressed his interest in the delicacy of the system of measurement, and asked if the micro meter had been used to d etermine the form of the plate when vibrating.

Mr. Phillips asked if experiments on the smallest sound audible had been made on different people, as it would be physiologically interesting to know if this minimum value were constant.

Mr. Campbell asked if the sound was expected when heard.

Mr. Shaw said be bad not conducted experiments on the form of the plate when vibrating, a lthough he had investigated its law of damping. He said the small sonnds were exp~cted, and the limit varied.

The Chairman said he found it easy to rid ga.l vano-meters and electrometers from extraneous d isturbance by placing them on a block of stone resting on a thickness of 3 fo. or 4 ft. of slag wool contained in a. hollow brick pillar.

The Society then adjourned until A pril 27, when t?e meeting will be held at eight o'clock in the 8 ola.r Phys1cs L aboratory of the Royal College of Science.

BLAST-F URNACES IN THE UNITED STAT&s.-The number of furnaces in blast in the United States at the commence-ment of March was 293, as compared with 257 at the com-mencement of September, 1899; 192 at the commence-ment of March, 1899; 186 ab the commencement of September, 1898; 193 at the commencement of March, 1898; and 161 at the comme~cement of Septembe.r, 1897. The weekly productive capa

MARCH 30, 1 goo.] E N G I N E E R I N G. =

THE " SENTINEL" AIR HOIST. CON TRUCTED BY MESSRH. ALLEY AND ~IACLELLAN, ENGINEER , GLA. GO'~'.

FlfJ .1.

.

' ' ' '

I

THE animated and prolonged discussion which has taken pla~e at the Institution of Mechanical Engineers at the last two meetings (see page 403 of this issue and page 280 of our issue of March 2) on pneumatic t ools, shows the great interest which is felt by engineers in these very useful and handy appliances, which pr?-mise to greatly reduce the amount of hand work 1n engineers' shops. We are quite certain to see a. very great increase in the use of compressed air in the im-mediate fu bure, particularly in the matter of light hoists, such as that illustrated above, which possesses several novel features, and which has recently been put on the market by Messrs. Alley and MacLellan, of the Sentinel Works, Glasgow. The cylinders for all sizes are of cast iron, and t he pistons and glandR leabber packed. In the top cover is formed a ball-and-socket joint which permits of the hoist being swung to a considerable angle in any direction. This, in many cases, increases the radius of operation of a. hoist , as it can collect its load from over a larger area. The construction of the operating valve is plainly shown in our illustrations. It is provided with a clear inqex-plate showing how t he valve has to be moved to lift or lower the load, and is worked by a T -handle, which in the larger hoists is fitted wit h two chains within easy reach of the operator. The plug or valve is separate from the spindle which is ~Slotted t o receive a projection on the plug. The latter is thus relieved of all jamming action due to the pull on the handle. The valve-works with perfect freedom and is abso-lutely tight. The object of the small supplementary exhaust passage or bye-pass in the valve shell will be seen later.

In the bottom cover are fitted two va.hres which form acombi~ed ai~-sa.ving and balancing device. The makers found, m usmg some old types of air hoists in their workshops, that when light loads which required t he

us~ of, say, only one-half of the pressure, were being ra1sed , when the piston reached the top of the stroke there was a great tendency to leave t he valve open t~ :'make sur~. " This. allo~ed t he full main pressure 1~to the h01st, resultmg m t he use of twice as much au as was required. In the " Sentinel ' ' hoist t he aotion is as !ollows : The operating valve being left open,. the l~etght of the lift is determined by the posi-t~on m wh1ch the small sliding collar is fixed to the ptstonrod by the operator. When the load has reached the desir~d. height, t he collar, rising against the C~OSBshaped shdmg sleeve, lifts the latter against a hehcal spring, raiRes the air-saving piston vahe

Firf .Z.

Bg.8.

-+ ! ---------- ---

+-+----::------ -

Fig.4 .

IJJJsl)

on the left-hand side, and cuts off the air supply. When a load is left for a considerable time at a fixed height, a small leakage of air may take place, and the piston-rod fall sligh tly , taking with it the adjustable collar. This allows the piston vahre to move down-wards, admitting air t ill the piston-rod again rises to shut off the supply as before ; the renewal of air lost by leakage is thus cont inually and automatically effected.

If the load should become lightened, as, for example, when metal is being poured from a ladle supported by the hoist, the air in t he cylinder expanding, raises the piston-rod, and the crosshead lifting the small relief valve to the right-hand side, allows t he excess of air to escape. By the action of the piston valve, the hoist cannot use more air than is necessary for a given load , and by the combined action of the valves, a varying load may be automatically balanced wit hin very narrow limits at any position of the lift. I t will be seen from our illustration that the piston valve when shut closes the exhaust from the main outlet. On reversing the handle to lower the load, release first takes place through the bye-pass, to which reference has already been made, and when the pressure in the hoist has been reduced the piston valve opens and allows the air to escape through the main outlet.

An air cushion is formed in the upper end of the cylinder by drilling a. small hole near t he top. The piston on nearing the end of its stroke blocks the hole, t he remaining a ir forming a cushion and bring-iug the load gradually to rest. In the event of a sudden failure of the air supply, the load is prevented running down by the automatic closing of the check valve in the top of t he vert ical air pipe.

These hoist s are made in sizes from 4 in. to 20 in. in diameter with lifts from 4ft. to 10ft., and of capacities from 5 cwt . to 10 tons.

STEINLE'S STEEL MERCURY THERMOMETER.

A COMPACT, handy , and reliable thermometer which will register temperatures up t o 950 deg. Fa.hr. has, we t hink, been a long-felt want; for, although there are many kinds of pyrometers which give more or leas accurate indications of temperature up to the point mentioned, they are not all of them as handy to use as might be wished. We think, therefore, that the Steinle steel mercury t hermometer, of which we annex illustrations, ought to fill a useful place in many

.,

processes where it is necessary to obtain correct tern peratures up to about 950 deg. Fa~r. .

The principle of the inst rumen t ~s as follows : A, tn F ig. 1, is a strong cylinder of nuld steel, called the "container " which is closed at one end, and tapers off at the oth~r to a very fine bore in a steel ~ire ~' the bore being less t han -h in. in diameter. Th1s oaptllary wire B may be of any length, from ! in. to 50 ~a.rds, and connects the container with n st eel spiral sprmg C. This spring consists of a solid-drawn steel tubo wit h t hin walls, which are rolled flat until they meet within 1 6 0 in., and are coiled as shown in the illue~rat ion. The container, t he capillary wire, and the aptral spring are filled with mercury, after which the upper end of the spring is hermetically sealed. The mercury is t hus contained in strong steel walls.

Now, if the mercury in the container is heated it ex-pands, and t he surplus volume is forced into the spiral spring causing it to par tly uncoil, thus making its free end rotate. If the temperature falls the mercury con-tracts, and t he spring moves in the opposite direction .

D

c

A

FIG. /.

' ... ~ ...

., . 'I I I "'

FIC.2.

D

I

The rotary motion of the spring is conveyed by means of the rod D, shown in Figs. 1 and 2, through suitable gearing to the dial-hand of an indicator, which is very similar in appearance to an ordinary steam pressure gaugP, and t he temperature can be read off with ease. These t hermometers are made in three principal types, viz. :

1. The rigid type, suitable for temperatures not ex-ceeding 300 deg. Fahr.

2. The rigid type, for temperatures up to 950 deg. Fahr.

3. The flexible type, with long capillary wire con-nection, which is available for any purpose or position, and any temperature up to 950 deg. Fa.hr.

We understand that these thermometers are very durable. W e ourselves tried one for some time, for taking t he temperatures of flue gases from a stationary boiler, and found it work very satisfactorily; it was also very easily applied.

The general agent for t he United Kingdom is Mr. Hermann Kiihne, 25-35, New Broad-street, London E.C. '

-

NOTES FROM THE UNITED STATES. PHII.A DRLPHIA, March 21.

T HE American iron and steel markets have gained strength very suddenly during the past few days. Up to a week ago, rumours and predictions of a decline in pri?~s were fre~uent. Later inquiries for l arge q_uant1t1es of matenal have been received and qu ota-tiOns have been m ade, but no particular importance was attached to this fact. Within a few days, bow-eve r, la rge orders have been placed for steel rails struct~ral material, billets, Bessemer pig, and othe; m atenals. The outlook is better than a week ago.

Ste~l rails ~re selling at 35 . dols. per ton. The proJected mtleage now ascertamed is close to 60 000 miles, a large. portion of which will be built j ust as soon as m atenal can be had. The extraordinary in-crease in traffic, the high margins made by most rail-roads, th.e excellent outlook for old rails in general, all contr1bute to encourage railroad building. The country is settling fast thr oughout the South and West .. Cotton in t he South has reached 9 cents so far, and in the West, cereals and meat stuffs have brought good prices. The agriculturists throughout the West and South a re preparing to cultivate a much larger area during the coming year. Again, the new Currency Law, passed by Congress, and signed by the President, shows an increase in currency amounting to several hundred million dollars. With this increase it will b e possible to do a good deal that otherwise would be impossible. The iron t rade is certainly in a good condition. Mills and furnaces are e\'erywhere over-sold. During the past three or four days large order s have come in, and a good many of them have been turned down. There were several orde1s from Europe for 10,000 tons of pig iron which could not be sold. Foundry iron is thoroughly active and will now be more active. Mill owners are making inquiry for large quantities of forge. Merchant bar mills are crowded up to about June 30. Structural mills are oversold under orders for bridge-builders. There is a heavy demand for old iron and steel rails, and prices have advanced 1 dol. a ton. All kinds of sk elp are wanted, and t he supply is below requirements. The financial situation is a ll t hat could be desired. The tinplate industry is in excellent shape, and the entire produc tion is bein g promptly marketed and sold. Copper is looking upward on account of the heavy demand, both at home and abr oad. There is nothing new in the coal trade beyond the fact t hat the stringency is perha ps more serious than was at first supposed . Coal will be considerably hig her, because of the ad vance in wages averages about 10 per cent.; the freight rates are considerably higher than last year. The four lea ding coal r oads delivering coal a long the Atlantic coast estimate a n increase of 16,000,000 dols. in freight rates by coal alone. The consumers have to pay t hi3 increase in profit.

NOTES FROM THE NORTH. GLASGOW, Wednesday.

Glasgow P ig-11'fYn Ma,.rket.-Business was fairly active on the pig-iron warrant market on Thursday forenoon, and the tone was very strong. Cleveland iron s till took the lead, being in active demand for Germany, and as the price was very much higher than that of local iron, little of it was being brou~ht in here, and Scotch iron was, therefore, being taken 10 its place. About20,000 tons were dealt in, and Scotch rose 9!d. per ton, Cleveland l s. l~d. , and bematite iron 9d. per ton. Scotch iron was within 2s. per ton of the highest _'Point touched last year (75s. 7 d. per ton), a nd Cleveland was 6d. under it l75s. 6d. ), while Cumber land hema-tite iron wa3 ls. 8~d . above the highest figure (80s . 1 ~d.) reached in 1899. In the afternoon some r ealising was engaged in, understood to be on London account, a.nrl prices lost the bulk of the forenoon gains, Scotch reaching 6i d ., Cleveland 6d., and hematite iron 2d. per ton. The sales amounted to 10,000 tons, and the settlement prices were : Scotch iron, 73s. per ton ; Cleve-land, 74s. 6d.; Cumberland and Middlesbrough bematite iron, 81s. 6d. and 82s. 6d. per ton. The market opened very flat on Friday, on cables received from America reporting a decline there of 1 dol. per ton in the price of p1g iron. There was a moderate recovery from the lowest poin t, but on the day Scotch lost ll! d. per ton, and hematite iron 9~d. Cleveland was not dealt in, and sellers' quotations were unaltered from those of Thursday. Only a small amount of business was done, and the closing settlement prices were: 72s., 74s., 80a. 9d., and 833. per ton. A moderate amount of business was done on Monday forenoon, and the tone was steady. About 15,000 tons changed hands, and Scotch rose 1d. per ton, and Cleveland 3d., but hematite iron dropped 3d. per ton. Close on 10,000 tons changed hands in the afternoon, and the tone was firm, especially for Cleve-la nd iron, which rose other 4!n. Thesettlementpri~es were: 72s. 3d., 753., 80s. 7~L, and 82s. 6d. per ton. On Tnesd}ty forenoon the pig-iron market was strong, with about 10,000 tons sold at appreciable advanGCs. Rcotch warrants gained 8d. per ton at 723. lO}d. cash, with buyers over. Cleveland which was not dealt in, was quoted l~d. per ton up at 753. cash buyers. Business was done in the afternoon ab 733. and 733. 2d. cash, and a t 73s. 5;d. per ton one month, and the settlement prices were 1

EN G I N E E RI N G. 73s. 4~., 75s. 9d., 8ls. 10~., and 82s. 6d. per toa About 15,000 tons of iron changed hands this forenoon. The tone of the market was exceedingly s trong, and great nervousness was shown by the "bears." Advances ranging from 7d. to ls. 3d. per ton were made. The sales in the ~fternoon .ranged between 10,000 and 15,000 tons, and pnces remamed very firm. The settlement prices were : _74s. Gd. , 77s., 82s. 6d. , and 83s. 6d. per ton. The followmg are the quotations for makers' No. 1 iron :

Clyd~, 84s. per ton ; Calder, 88s. ; Summerlee and Gart-sherne, 90s. ; Colt ness, 90s. 6d. per ton-the foregoing all shipped at Glasgow; G lengarnock (shipped at Ardros-sa.n), 83s. 6d. ; Shotts (shipped at L eith), 88s. ; Carron (shipped at Grangemouth), 87s . . per ton . T he follow-mg are the returns of the shipments of Scotch pig

iro~ for the week ending last Saturday : For the Umted States, 125 tons; for S outh America, 164 tons ; for India, 210 tons ; for Australia, 844 tons ; for Italy, 1810 tons ; for Germany, 640 tons; for Holland, 500 tons; for Belgium, 110 tons; for Spain and Por-tugal, 150 tons ; for China and Japan, 100 tons ; smaller quantities for other countries, and coastwise, 5292 tons, the total for the week being 10,285 tons. The heavy re-duction in stocks, a nd the grea t scarcity of iron in every district, induced considerable "bear" covering, and to this much of the excited buying lately prevalent can be traced . On Friday the first react10n during this upward movement occurred, when prices reacted l a. per t