88 .Editorial ~orresTondence.

led to admit that the phosphoric acid in the meta, pyre and ortho phosphoric acid is not the same, but that there are in these bodies substances as distinct as are sulphurous and sulphurie acid. Thus H PQ, H~ POT, H3 POs. This is altogether contradicted by the pro perties of the acid, the characters of its salts, and the facility with which they assume and part with the elements of water, being thereby transformed, the one into the other. The many other ob- jections in point of fact and reason, need not be stated. The type theory, so well suited to the study of the complex and therefore elastic substitution compounds of organic chemistry, is illy adapted to the simpler and less flexible bodies, generally included under the head of inorganic chemistry. Thus, to represent the pyre-phos- phates, we must assume four molecules of water as the type, thus

tI4 (using molecular symbols) 1~ 04. Then "pyre-phosphate of sodium"

:Na~ :Na2H ~ 1 would be (P2 03) " 'O4 and "acid phosphate of sodium" (p203),,,r ~ 0 c

(Bloxam's Chemistry, p. 256). What a contrast to the simplicity of the "ancient" formula 2 NaO, P Q ; :N'aO, t t O, PO 5. What is gained by the change ?

It is not necessary to add more, I only wish to show that there are reasonable grounds for holding certain theoretical views which are by some believed to be accordant with facts, and certainly much more simple than those by which it is sought to replace them.

B. HOWARD RAND, M.D.

Editors of the Journal of the Franklin Institute. Ix my paper entitled "Experiment on the Evaporation of a Cor-

liss Boiler," in your number for June last, I quoted erroneously from table II. in the Description of Richard's f~proved Steam .En- gine Indicator, by taking the temperature of saturated steam, corre- sponding to the pressure above the atmosphere, as if it was the total pressure. The temperature corresponding to the pressure of 66"46 pounds above the atmosphere should read, 3!2"9~ a. The mean observed temperature of the steam being 311"80 °. It appears that the steam was not superheated, and of course the small additions to the observed evaporation, made in the paper, on account of superheating, should bc omitted. JAM~S B. F~A~cls.

Lowell, :Mass., June 80, 1870.