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NARURE 
99 
exhaustive and yet lucid and interesting from beginning 
toend. After reading it one feels that the Deinocerata 
are no longer extinct, vanished forms, but familiar ac- 
quaintances which one could not fail to recognise any- 
where. Every part of their structure is methodically 
presented to view, and restorations are given showing the 
relations of the parts to each other and what is the 
author’s conception of the general form of the animals. 
It has hardly ever been possible in the Old World to re- 
construct the mammalia of so early a period from such 
ample materials as are now amassed at Yale College. 
Hence the restorations attempted have often been little 
more than more or less probable conjectures which might 
be conformed but were more usually corrected or even 
effaced by the progress of discovery. So full, however, is 
the evidence for Prof. Marsh’s restorations, that there 
remains very little room for future emendation. He is 
still engaged in continuing these remarkable memoirs on 
the ancient life of the North American continent. A 
third monograph on the Sauropoda is approaching com- 
pletion, and a fourth, on the Stegosauria, is far advanced. 
These large and profusely illustrated works are issued as 
part of the work of the United States Geological Survey. 
They reflect the highest honour on their indefatigable 
author, and on the Survey which undertakes their publi- 
cation. ARCH. GEIKIE 
REMSEN’S “ORGANIC CHEMISTRY” 
An Introduction to the Study of the Compounds of 
Carbon; or, Organic Chemistry. By Ira Remsen, 
Professor of Chemistry in the Johns Hopkins Uni- 
versity. Pp. x., 364. (Boston: Ginn, Heath, and Co., 
1885.) 
ae is chemistry. Of how few books professing to 
be books on chemistry can it be said that they 
teach us anything of the science. The student who 
begins the study of the carbon compounds has to suffer 
many things from the text-books. Some of them present 
him with dry bones in the shape of isolated facts and 
bold assertions regarding structural formulae and the 
linking of atoms. Others Jead him into speculations 
which he is unprepared to follow ; he makes little flights 
into these and comes back fancying he is a chemist. 
Other books (there are not many of them) proceed on the 
true scientific lines ; but very frequently their pages are 
encumbered with too many facts about more or less 
widely separated compounds, or they deal so much with 
groups of compounds, rather than with typical individual 
bodies, that the beginner soon loses his way, becomes 
perplexed, and is ready to abandon the pursuit. 
Prof. Remsen has shown us a more excellent way than 
any of these. He leads the learner by degrees through 
the early difficulties; he places before him distinct and 
detailed accounts of a few typical compounds ; he shows 
him how these compounds are mutually related; and 
then he takes him back to the beginning again and teaches 
him how each compound he has learned to know repre- 
sents a group, and how, when he knows the properties of 
one member of the group he also knows much about all 
the members. 
At the outset Prof. Remsen makes a few wise and 
pregnant remarks on the meaning of structural formule. 
These “ enable the chemist who waderstands the language 
in which they are written to see relations which might 
easily escape his attention without their aid. In order 
to understand them, however, the student must have a 
knowledge of the reactions upon which they are based ; 
and he is warned not to accept any chemical formula 
unless he can see the reasons for accepting it.” The 
whole book is a practical sermon on this text. 
In no other elementary book in the English language 
will the student find so many admirably chosen examples 
of the formation of structural formulz. The important 
facts are noted ; then the inference is drawn; then the 
hypothesis is ventured upon; analogous facts are re- 
called ; the hypothesis is strengthened or weakened ; 
suggestions are made ; experiments are conducted ; and 
all is finally summarised in the formula. But the book is 
more than a selection of examples showing how s‘zuctural 
formule ought to be gained. It is a systematic although 
elementary treatise on organic chemistry. The student 
is first taught about the two paraffins, methane and 
ethane ; then he learns how the halogen derivatives of 
these are prepared, and what relations they bear to the 
parent hydrocarbons. By this time he has had his first 
taste of isomerism. Then he proceeds to the oxygen 
derivatives of methane and ethane; he learns what an 
alcohol is ; he becomes acquainted with ether, aldehyde, 
formic and acetic acids, some ethereal salts, and acetone. 
This method of studying a few simple compounds in 
detail is pursued until the student is more or less familiar 
with representatives of all the principal groups of com- 
pounds derived from the paraffins. He is now in a 
position to study these hydrocarbons as a group, and to 
deal in some detail with the questions of isomerism. 
When the paraffins and their derivatives have been thus 
studied, the more difficult subject of the benzenes and 
their compounds is approached. And here the author 
shows an admirable power of dealing with facts as facts, 
and with theories as theories. What could be better than 
the following remarks regarding saturated and unsaturated 
compounds ? 
“In the aldehydes and ketones, carbon is in combina- 
tion with oxygen in the carbonyl condition. When they 
unite with hydrogen and some compounds, such as hydro- 
cyanic acid, the relation between the carbon and oxygen 
is probably changed, the latter being in the hydroxyl 
condition. The changes are usually represented by 
formulas such as the following :-— 
CH,-C7 2 +H, = CH,.c¢ OF 
H.€ re 
3 H3C\, J 
C=OfHEN= (7 eCN, 
H,C/ H;C/ 
In the carbonyl group the oxygen is represented as held 
by two bonds to the carbon atom, while in the hydroxyl 
condition it is represented as held by one bond. The 
signs may be used if care is taken to avoid a too literal 
interpretation of them. There are undoubtedly two rela- 
tions which carbon and oxygen bear to each other in 
carbon compounds. These relations may be called ‘he 
hydroxyl relation, represented by the sign C—O—, and 
the carbonyl relation, represented by the sign C=O” 
(pp. 209-10). 
How different this is to the crude, glaring statements 
that annoy the reader of the commonplace text-book 
written by the Philistine. 
The fact that structural formule help us to understand 
the relations existing between the parts of specified mole- 
