liei'iew of Recent Geological Lit era tun;. 195 
in this way, mixing in all proportions at high temperatures, and on 
partial cooling may separate into two or more parts by liquation. The 
author then selects two cases, basic inclusions and the great petro- 
graphical province of Iceland, and examines them briefly in the light of 
both theories, i. e., differentiation due to Soret's principle and that due 
to liquation. In these cases the latter theory seems to explain the facts 
bette^ . "The purpose of this communication is to give to liquation and 
not to diffusion its place in the working hypothesis, upon which the 
theory of differentiation is to be constructed. How far this theory may 
differ from the approximation to it given by Rosenbusch in his 'Kern' 
theory, the future will show." G. 
Genetic Relationships among Igneous Socles. By Joseph P. Id- 
dings. (Journal of Geology, vol. i, No. 8, pp. 883-844, Nov.-Dec, 1898.) 
Under "Studies for Students" Prof. Iddings has presented in a clear 
and simple manner some of the data and opinions bearing upon the 
genesis of different kinds of rock magmas. The results of differentia- 
tion, the gradual passage from one rock type to another and the 
sequence of eruptions are briefly discussed, and special attention is di- 
rected to the existence of distinct and well characterized petrograph- 
ical provinces. A distinction is noted between the idea conveyed by 
the term rocks as ordinarily used and that which is involved in the ex- 
pression rock-body as a geological unit. G. 
Annals of British Geology, ls!>2. A digest of the hooks and papers 
published during the year- loith occasional notes. By J. P. Blake. 
(Pp. i-xliv, 1-310; 7 plates; 8vo: Dulau & Co., London. 1898.) 
This book gives a compilation of all that has been written on the ge- 
ology of the British Isles during the year 1892. The various articles 
are divided into different groups and under each title is an abstract 
giving the gist of the article; sometimes these abstracts are several 
pages in length. Many of the abstracts have been submitted to the 
various authors for correction and approval, and in such cases this fact 
is indicated, thus making the abstracts all the more valuable. The au- 
thor has wisely refrained from indulging in any discussions or criticisms 
of his own in connection with the abstracts; such discussions and 
criticisms are brought together in the form of introductory review. 
Among other things in this review it is noticed that the results as to 
the recentness of the end of the Glacial period, obtained by a study of 
the recession of St. Anthony falls and of Niagara falls, are questioned, 
and the author concludes : "If, then, the American glaciation only dates 
back as far as that (7,000 years), it cannot belong to the same period as 
ours; there must have been two glacial epochs, one in the old world and 
another in the new." All the new species of British fossils described dur- 
ing the year, except those in the Palajontographical Society's volumes, 
are figured and aselection of other illustrations is made. This book repre- 
sents a great deal of work and will be a valuable aid to all geologists, 
especially to those who do not have access to a library whicb contains 
the recent geological literature. G. 
