512 



Revvncs — Fock's Chemical Crystallography. 



the air, or may have fallen with the wind that preceded a second 

 snowfall. At any rate, it was found afterwards forming a layer of 

 dirty snow, between two clean layers of snow, and it was thus easy 

 to gather it free from the underlying soil. A large number of 

 specimens were collected and were submitted to microscopical and 

 physical examination. The dust was found to be largely made up 

 of silt, mixed with organic matter, and was probably derived from 

 some dried-up lake, pond, or marsh to the north-west. Professor 

 Whitney's mechanical analysis shows that it is almost identical with 

 the loess that covers great areas in Illinois, Nebraska, and other 

 adjoining States, and he gives the following Table showing the 

 percentage hy weight of the contents of air-dried samples : — 



The different estimates of the amount of dust that fell vary from 

 12|^ to 150 lbs. avoirdupois per acre. C. Davison. 



I^ IE "\^ IIE ^SAT" S. 



I. — Chemical Crystallography. An Introduction to Chemical 

 Crystallography. By Andreas Fock, Ph.D. (Berlin). Trans- 

 lated and edited by William J. Pope. (189 and xvi pages, 

 8vo.) Clarendon Press, Oxford. 



MASKELYNE'S "Morphology of Crystals" has been quickly 

 followed by a companion volume issued from the same Press, 

 and dealing, not with the geometrical form, but with the origin, 

 growth, and chemistry of crystals. In a review of the former book 

 it was stated that Crystallography has now developed relationships 

 with other sciences, by which it is invested with numerous practical 

 applications. Fock's little book should be read by everj' chemist 

 or geologist who wishes to have a thoroughly lucid and reliable 

 account of the manner in which crystallography dovetails into 

 chemistry, and especially of the remarkable problems which have 

 emerged into prominence during the last few years in the region 

 of physical chemistry. Some of these have come into existence 



