Sa it cee 
Geology. 273 
tical table of the various floras, indicating the order of their hha 
logical Succession and their mode of distribution in the various 
formations to which they belong; and, in the fourth part, a biblio- 
graphical index of vegetable paleontology from the beginning of 
the century to the present time.* 
It would be possible to criticize some of the opinions of the 
European author, or to point out a few errors in the discrimina- 
tion of our American species. But Prof. Shimper has come to 
his general conclusions from a peculiar point of view sustained b 
an immense array of facts, in whose examination we cannot follow 
him, and the few omissions and errors of descriptions remarked in 
his book will certainly be corrected at the end of the work. We 
“rof. Shimper’s treatise is written in French, in an elegant style, 
which though concise, is clear and easily understood. Only the 
diagnoses of his genera and species are in Latin. L. 
3. On the Physical Cause of the Motion of Glaciers ; by JamEs 
ility of the Descent of Gla- 
ice over one another and alongside one another, to which is op- 
Posed that force of resistance which is known in mechanics as 
shea, rin Jfore e.? 
te determines by calculation the amount of shearing-force 
Which must not be exceeded if the displacement of the particles is 
*The details on the unpublished volume are translated from the Publishers’ 
onan L. B, Baillidre et din, ise is published as 
