Chemistry and Physics, 481 
‘greatly to illustrate. Persulphuric oxide is an example of 
a 
remarkable class of compounds Se formation is attended with 
the absorption of heat, and whose production can only be deter- 
mined by the expenditure of some mode of energy. Correspond- 
ing to these circumstances of their genesis are the facts that these 
compounds are very unstable, and that when they decompose into 
more stable products the heat previously rendered latent becomes 
ree. Now in accordance with the mechanical theory of heat we 
are forced to the assumption that the expenditure of energy attend- 
ing the production of such unstable compounds gives to the parts 
of their molecules a certain energy of position, which energy 
investigation. We find it therefore difficult to understand why it 
is that M. Berthelot, while furnishing chemistry with some of the 
most important facts on which the modern theories of molecular 
structure are based, should so ae, el gop al the results of 
those who are investigating t he same subject f a different 
point of view, and whose conclusions are, at ibasts as ; tantworhey 
as his own, In the present series of Peper, Ann, de Chem. et 
Phys., July, 1878, Dammes theory of types i a perayeu nd advoca- 
ted as more philosophical than the peiaoiy os ved doctrine of 
atomicities, on the ground that it is not so much the nature of the 
radicals as the so-called type of combination which determines 
the qualities and chemical relations of the reqntang Bi hn 
But in the present state of science what conception can we form 
doctrines Berthelot condemns, are ct engaged on the one aia’ 
ical types, and it must be admitted that the value of a working 
theory ies solely on its power of correlating — 
10, Acous n a recent number of the ‘Philosop 
ical Magazin 
a ha 
tember, 1878, p. 225.) The scien is a rene that the reson- 
the area of its aperture an 
Am. Jour. 8c01.—THirD — Vou. XVI, No, 96.—Dzc., 1878, 
