322 REVIEWS 
have been held concerning the variations, championed by De Saussure 
and Gay Lussac. A statement of these two opposing views can best 
be summed up in the words of the authors. 
According to the first of these [De Saussure], considerable variations in 
the amount of atmospheric carbonic anhydride occur, of a more or less last- 
ing or permanent nature, caused by natural agencies such as the seasons, 
influence of vegetation, the direction and force of the wind, humectation and 
desiccation of the soil, day and night, etc. 
Gay Lussac, on the other hand, was of opinion that owing to the con- 
tinued movements of the air, both horizontally and vertically, practically 
uniform distribution or diffusion of the carbonic anhydride occurs. It must 
be at once granted, from the evidence which has since been forthcoming that 
Gay Lussac’s opinion is correct to the extent that the variations are much less 
than De Saussure and others of his school believed and that the average 
amount of atmospheric carbonic anhydride is much the same under the most 
diverse conditions of weather, locality, season, etc. 
The authors state, on the other hand, that variations of a lasting 
kind do occur, amounting to at least as much as io per cent. of the 
total quantity. 
Variations in the atmospheric carbonic anhydride are discussed by 
the authors under the following headings: (a) Locality and local 
effects. (6) Day and night. (c) Influence of vegetation. (d@) Influ- 
ence of atmospheric precipitates ; (1) fog and mist; (2) rain and snow. 
(e) Influence of wind. (/) Influence of the seasons. (g) Influence 
of cloud and sun. (f#) Influence of height. 
The figures obtained by various investigators bearing on each one of 
the above headings are brought together in tabular form, reviewed and 
criticised, and conclusions when warranted are deduced. 
While the subject of variation of atmospheric carbonic anhydride 
has been one of long-continued investigation and a wealth of figures 
accumulated, the results are lacking in uniformity, and more often 
have been carelessly obtained, and are therefore unreliable, and very 
often lead to opposite conclusions. Much remains to be done in the 
way of careful and uniform observation and determination by reliable 
and painstaking workers before definite conclusions may be looked 
for. From the mass of figures given by the authors the tendency, 
however, is certainly strongly in favor of Gay Lussac’s opinion, that is, 
the distribution of atmospheric carbonic anhydride is more uniform 
and the variations not so great as was formerly held by many. 
