Nr. 372. 188 187

*) Dus Herausziehen des Oculars in dem einen Fallc um 4’125 Pr. bei 1 4 ~ Focaldistanz gkbt cine ongefahrc Entfernung von f,f,Oo Furs, und wcgen 15’ Hiihe iiber dem Horizont 1700 Furs Hiihe iiber der Erdoberfliche.

fliegende Sommer sei. Am Iden und 17tcn September beweg- ten sie sich so langsam, dars ich mehrere derselben bis 50 Entfernung von der Sonne verfolgen konnte. Hier legtc ich das ( nicht angeschraubte) Sonrienglas weg, zgg das Ocular weiter heraus und bekam dadurch ein schiirfcr hcgrriiztes Bild *). Sic erschienen meist als lingliche mil kleinen Sciten- ansatzen und TJnebenheiten versehene Kiirper , weifslich und durchscheiiiend, untcn abgerundet, oben spitz und in einen Faden verllngert. Sie machten langsame Kriimmuiigen und S firmige Biegungen , und erschienen iii versehiedenen Pro- jectionen rerkiirzt und verlingert. Oft rvaren zwei durch einen Faden verbunden, die sich um einander drehten, auch isolirte Fiiden zogen voriiber, die das ganze Gesichtsfeld ein-

. v

wird einfach dadurch bewiesen , dafs im Fernrohr und Sucher gleichzeitig erschienen, welchen Versuch der Herr Prof. Encke die Giite hatte in Gemeinschaft mit mir anzustellen.

nahmen. Zwar habe ich iibereinstimmend mit den Erfahrungen des Herrn Hofraths Schruabc (Astr. Sachr. Nr. 350) an Tagen, wo die Lichtflocken selir hlnfig waren, keinen fliegenden Sommer gesehen , und umgekehrt. Dagegen macht ~ f r a g o (Ann. Ch. et Ph. XXX. p . 471) gerade auf die Gleichzeitigkeit bcider Erscheiiiuugen aufmerksam. Auch kijnnte es wohl sein, dafs der fliegende Sommer bei verschiedenen Zustanden der Atmosphare in verschiedenen Hijhen flicgt.

Dafs alle Lichttlocken fliegender Sommer seien, folgt zwar aus den obigen Wahrnehmungen noch nicht, man wird sie aber bei der Gleichartigkeit ihres Ansehens immer fGr iihnliche in der Luft fliegende Fasern oder Staubtheilchen zu halten Ur- sache haben. D a b die Erscheinung keine optische Tauschung, iioch im Focus des Fernrohrs zu suchen sei (vgl. A. N. 11’1.. 144)

Brief des B a r o n e t s , Sir John F. W . HerscheZ an d e n Herausge ler . Slough, Jan 19. 1839.

T l i c star 7 Argus about which you enquire, was materially diminished in lustre before I pit ted Africa and the diminution was progressive tip to the last time that I saw it, which was on the 14th of April (in Lat. 17°--180 N.) at which time it had lost so much of its lustre as to rank between

Orionis and Aldebaran, whereas at its maximum on the 2 8 t h Dec. 1837 it was scarcely inferior to oc Centauri which, after Sirius and Canopus is beyond all comparison the brightest star in the Southern Hemisphere, and which ranks somewhat above Arcturus the brightest of our -Northern Stars. Since my return to England I have had no report of the progress of this remarkable phamomenon.

Being on the subject of the brightness of the stars, I should be very glad to see the attention of astronomers re- called to the subject of estimations by the naked eye, after the manner of my Father’s catalogues of comparative bright- ness , but without confining the comparisons to separate con- stellations, as I am convinced that not only many more perio- dical stars will thereby be discovered, but that changes not periodical will be found to prevail to a very much greater ex- tent than is now supposed, and which I would suggest may be accounted for by superadding to Olbers’s idea of imperfect transparency in the celestial spaces, that of inequality in the degree of opacity of different regions, and of movements going on in the opake matter whatever it be. In short by supposing

the existence of some sort of cosmical c l o u d i n e s s subject to internal niovenients depending on causes of which we are ignorant. Of the nature of these super - atmospheric clouds of course no conjecture can yet be formed, but seme argument for their being of a material nature may be drawn from the strange observation of Ptolemy that Sirius was in his time one of the 6 red stars, classing it with Arcturus, Aldebaran, Pol- lux, Antares and CL Orionis by the common Epithet dadxrppor. It seems much more likely -that a red colour should be the effect of a medium interfered than that in the short space of 2000 years so vast a body should have actually uuder- gone such a material change in its physical constitution.

Being on this subject I may notice aHydrae as certainly a periodic and oc Cassiopciae as a variable star. At least, in Novembre last, I observed y to be very decidedly the prin- cipal star in that constellation, whereas at present a is as it was in my Father’s time, the brightest of the three a, p, y. I am also disposed to agree with Struve who in a letter I Rave lately received from him seems to consider Capella as on the increase. Certainly on my return to the Northern Hemi- sphere I was surprised to find that a higher place must be assigned to Capella than I had mentally (from recollection ) ascribed to it when engaged in arranging the Southern stars.

Turning up authorities on this highly interesting subject, I was greatly surprised to find the following numerical propor-

189

- Siiius - 4102 Canopus = 2281 cecentauri = I000 Arcturus = 744 Rigel - 742 aEridani = 519 pcentauri = 426

-

Nr. 372.

ctcrucis = 381 a Aquilie = 357 ,13 Crucis 263

yCrucis = 207 a Gruis = 179

etc.

&Canis = 219

lions between the light of Southern stars assigned by Hum- (loldt ( Tilloch's Philosophical Magazine, Jan. 7. 1802. Extract of a letter to LaZamZe).

Sirius = 100; Canopus = 98; acentauri = 96; a Eridani = 94; Procyon = 88; oc Gruis = 81 ; a Pa- vonis = 78; etc. etc. , ,I employed the method proposed by Dr. F€erschd and diaphragms of the same kind as those used for the satellites." Now these numbers, even on the mere rough estimate by the naked eye appear to me so very erroneous that I am at a loss what to make of them, nor can anything set in a stronger light the extreme difficulty of procuring numerical measures of star light, than the fact of their ever having been obtained by an observer usu- ally so very careful and exact. For my own part I cannot estimate the light of Canopus as much more than half that of Sirius, and the step from Canopus to oc Centauri is fully as wide as that from Sirius to Canopus. Again I make by actual measurement, on a principle open I thirtk to no theoretical objection, though attended with some trouble in practice, I make dc Eridani only half a Ccntauri instead of being to it i n the ratio of 94 to 96 a s Humtrolclt inakes it etc. etc.

He says

Perhaps too 1 may be pardoned if, without at all in- tending to criticise the ingenious and elaborate instrumental contrivances of ICI. Steinheil, I take this opportunity of clraw- in$ his ;ittetitiori (slroiild you Ihirtk these rcrnaiks worthy of ;I lilacc i i i tlrv Kiiclrric*lrtcli) to oirc or two cases iir the list of relative magnitudes given in p. 24 of his work (Elemente der Helligkeits - Rlessungen etc.) where if 1 mistake not comparison of the stars by the naked eye would have led him to hesitate about thc adoption of the numbers assigned. Thus, he places Spica considerably above Rigel, Procyon above Capella, Re- gulus above Aldebaran and makes Spica arid Capella very nearly equal.

pitain w. Nyeyaarrl, R. v. D., tlcr bei clrri niir Sllerh6chst ubertragenen Vermessungen angestellt i d . diis Kitterkreuz des Schwerdtordens , und Herrn Observator Petersen das Ritter- kreuz des Wasaordens zu verleihen geruht.

9. Slaminski, Director der Wilnaer Sternwarte, den St. Anneri- orden 2ter Klasse , und dcin Herrn Hdowchnevitch, Observator an der Wilnaer Sternwarte, den Stanislausorden 4 t e r Klassc mid

einen Brillantring zu verleihen geruht.