REVIEWS. 
The Carbonic Anhydride of the Atmosphere. By PRoFeEssor E. A, 
errs, DSc iPhDe and: Re, hie sR Aker oan GaSe 
(Plates XVI to XVIII). The Sctentific Proceedings of the 
Royal Dublin Society, 1900, Vol. X(N: 15%); Part) Vit app: 
107-270. } 
THE memoir is divided and separately treated in two parts, the 
results of which can best be summarized under each division. The 
extensive review and criticism by the authors of the literature on the 
amount and causal distribution of atmospheric carbonic anhydride 
added to the widespread importance of this constituent in aiding cer- 
tain geological processes, warrant a detailed review of this very valuable 
paper. 
PART I. 
Section I is devoted to the “Introduction and Methods of Deter- 
mination.” The first demonstration of the existence of carbonic anhy- 
dride in the air was by Dr. Black, of Edinburgh, probably between the 
dates 1752 and1754. Many different processes have been employed 
since De Saussure’s time (1796) to determine atmospheric carbonic 
anhydride, but only the more important ones are considered in this 
paper. The authors state that with the exception of several methods 
based on the physical properties of gases, all the processes depend on 
the employment of an alkali or alkaline earth as an absorbent ; and 
the amount of carbonic anhydride absorbed is determined by one of 
several methods, among the most important of which are : (1) increase 
in the weight of the absorbing apparatus ; (2) determination of the 
excess of the absorbent ; (3) liberation and measurement of the absorbed 
carbonic anhydride. A rather extended review of the work of numer- 
ous investigators following these methods, in which the more essential 
points in each method as developed by the individual worker, are 
brought out and discussed in a brief manner. 
Section II is a description of ‘‘The Authors’ Experiments on Pet- 
tenkofer’s Process as Modified by Them.” A set of determinations 
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