6 
REVIEWS 625 
With these data it is not difficult to calculate the effect of any change 
in the amount of carbon dioxide upon the temperature of the surface 
of the earth. The temperature of the earth’s surface is theoretically in 
equilibrium with that of the atmosphere. Now if by any increase in 
the amount of the carbon dioxide the atmosphere retains more heat 
than before, it will radiate more heat to the surface of the earth. ‘The 
‘surface temperature then will rise until there is again an equilibrium 
between the two. This rise is governed by Stefan’s law which states 
that the intensity of the radiation is proportionate to the fourth power 
of the er 
From these data Professor Arrhenius finds that if the carbon dioxide 
is increased 2.5 to 3 times its present value, the temperature in the 
arctic regions must rise 8° to 9° C. and produce a climate as mild as 
that of the Eocene period. A diminution to 0.62 to 0.55 of its present 
value must cause a fall of from 4° to 5° C. and give us a glacial period. 
It is to be noted that in every case throughout the calculation Pro- 
fessor Arrhenius has preferred to slightly underestimate the effect of 
the carbon dioxide than to risk a possible overestimate. Also where 
he has been compelled to use interpolation the limit of error has been 
well within the degree of accuracy of the observations upon which they 
are founded. 
The tremendous interest of these considerations, not only as a basis 
for the interpretation of the past history of the globe but also for the 
prophecy of its future, demands an investigation of the problem along 
the lines of direct experiment, as a supplement to the elegant calcula- 
tions of Professor Arrhenius. Cyrus F. Touman, Jr. 
Special Report on Gypsum and Gypsum Cement Plasters. By G. P. 
GrimsLey and E. H. S. Baitey. University Geological 
Survey of ‘Kansas, Vol) V. Pp. 183,30 plates. Topeka, 
1899. 
Among the minor mineral industries of the country those connected 
with gypsum have been, so far as literature is concerned, heretofore 
neglected. The present report is accordingly particularly welcome. 
‘The papers so far accessible have been, in the main, devoted to the 
description of local deposits and the technology of the gypsum industries 
has not been described before in any adequate manner. ‘The present 
volume includes not only a description of the Kansas gypsum. beds 
