oe . > + ps 
terms “hydroxide” and “anhydride” -have been php ae 
“gua; by Groran H. Jounson, Professor of Ma 
_ George H.’Cook, of New Brunswick, N. J.,and comm 
Geology and Natural History. 239 
than to that which it is intended to represent. In consequence 
of this truth, it has happened that a large number of chemists 
have regarded the determination of a formula for a compound as 
the great object to be accomplished and forgotten that what we 
ought to know and what is of vastly greater importance for the 
Science is the chemical conduct of the compound.” Hence the 
author states in the preface: “I have endeavored to discuss in an 
impartial way, as objectively as possible, the principal hypotheses 
which at present play important parts in the science of chemistry. 
As, strictly speaking, we have no theory of chemistry, the hypoth- 
€ses are more or less disconnected; and as there is no general 
theory to keep them in check, some of them have assumed a vari- 
ety of forms.” What, precisely, is meant by the term “ constitu- 
tion” on the title page, he tells us on page 232: “A study of 
the preceding chapters on constitution will show that no absolute ; 
meaning is to be attached to the word. Constitutional formulas 
are those which suggest certain reactions and recall analogies. 
The formula CH,—OH does not mean that hydroxyl (OH) is nec- 
~€ssarily present in the compound or that CH, is. present, but that 
the different parts of the compound bear such relations to each, 
Other that when the compound is decomposed it acts as if the 
parts were united as the formula indicates. The formula suggests 
Possibilities; it may not represent realities.” The book is there- 
fore a valuable contribution to the chemical literature of instruc- 
ees and particularly at this time when so strong a tendency 
Cal reactions, 
talled for indicates that many chemical teachers have been found 
ready to endorse its plan and to adopt its methods. In thisedi- 
tion a considerable proportion of the book has been rewritten, : 
up to date. We observe 
Place of the simpler ones “hydrate” and “oxide,” whic “We 
e 
te ae 
theory combined with the fullness with which, ina small com- — 
Pass, the present attitude of chemical science towa 
tution of j { 
Yond that accorded to the average text books of the day. 
Il. Gronogy anp Natura History. 
te Human Joot-prints on sandstone near Manaqua, in. Ni a 
thematics and — 
(From a letter dated Osties : 
n Leon, N icaragua, Central Am., Noy. 5, 1883, to ia essor a 
' 
Sineering at Leon, Nicaragua. 
ee % 
bea i 
