i88i.] 
Analyses of Books . 
679 
in which the early history of organic chemistry is sketched, with 
especial reference to the gradual changes in theory. Here we 
notice a curious clerical or typographical error : we read “ The 
early ideas of Van Helmholt and afterwards of Stahl.” The 
authors evidently mean to say “ Van Helmont.” After discussing 
the definitions of organic chemistry proposed in the earlier part 
of the century, and remarking that “ at the present day the belief 
in a special vital force has ceased to encumber scientific pro- 
gress,” the authors define this portion of their subjedt as “ the 
chemistry of the hydrocarbons and their derivatives,” — a more 
precise notion than, as was once proposed, the “ chemistry of 
the carbon compounds.” 
We next come to an elaborate and thoroughly illustrated chap- 
ter on ultimate organic analysis, to which is appended an account 
of the various methods of determining vapour-densities, as 
adopted by Dumas, Gay-Lussac, Hofmann, and Vidtor Meyer. 
In the sedtion on empirical and rational formulae we meet with 
the profoundly philosophical remark, ascribed to Kekule, that 
“ the true aim of chemistry is not so much the study of the 
existing substance as that of its past history and its future deve- 
lopment.” This point of view in one sense approximates che- 
mistry to biology, as studied in the light of the dodtrine of 
Evolution. 
After discussing isomerism, metamerism, and polymerism, the 
authors proceed to classify the carbon compounds under four 
great heads : — the fatty group ; a nameless group of unsaturated 
compounds, containing relatively less hydrogen than the above ; 
the aromatic group ; and a mob of compounds of unknown con- 
stitution which the progress of research is daily reducing in 
number. Into the description of the bodies belonging to these 
classes there is the less need for us to enter, as wherever we 
have turned we recognise the accuracy which the eminence of 
the authors warrants us in expedting. 
Concerning formic acid we may remark that the occurrence in 
the animal world is far more common than chemists seem to 
have recognised. It not impossibly stands in a close relation 
with the poisonous secretions of scorpions, centipedes, spiders, 
&c. Its great value as an antiseptic (referred to on p. 274) is a 
point which has been overlooked by sanitary reformers. As 
being at once more powerful than phenol, and free from the un- 
pleasant odour of the latter, its industrial preparation on the 
large scale ought to attradf the notice of chemical manufac- 
turers. 
The occurrence of common or ethylic alcohol in Nature — some 
cases of which are here mentioned — will be for many readers an 
interesting, and for others an unwelcome, fadL Concerning the 
so-called “ methylated spirit ” the authors justly remark that it is 
“ unfit for human consumption.” Nevertheless, except a very 
stridt watch is kept in establishments where this spirit is in use, 
