556 T. C. CHAMBERLIN 
On the other hand, an increase in the absorptive factors renders 
ineffectual, in a corresponding degree, the variations of altitude, 
of latitude, of land and sea, of day and night, and of the seasons, 
and conduces to an equable and mild temperature, to gentle and 
yet thermally effective circulation, and to higher average tem- 
perature. As Arrhenius has remarked, “ The geographical, 
annual, and diurnal changes of temperature would be partly 
smoothed away if the quantity of carbonic acid was augmented. 
The reverse would be the case (at least to a latitude of 50° from 
yy 
the equator ) if the carbonic acid diminished in amount. 
AGENCIES OF DEPLETION AND ENRICHMENT 
It now becomes necessary to assign agencies capable of remov- 
ing carbon dioxide from the atmosphere at a rate sufficiently 
above the normal rate of supply, at certain times, to produce gla- 
ciation; and on the other hand, capable of restoring it to the 
atmosphere at certain other times in sufficient amounts to pro- 
duce mild climates. : 
These agencies on both sides belong to two classes, the per- 
manent and the temporary, and the distinction has practical 
importance. 
Sources of permanent loss — Permanent depletion results from 
the consumption of carbon dioxide in the transformation of the 
silicates of the original earth, and of volcanic products into the 
carbonates of the secondary strata. It is fairly safe to assume 
that the original earth’s surface was composed of material of the 
general class represented by the igneous rocks and the basement 
complex. These, it is needless to say, consist largely of silicates 
with which are associated certain quantities of certain gases to be 
considered more fully hereafter. These silicates, where exposed 
to the weathering action of the atmosphere, become decomposed 
and take the form of carbonates (with less quantities of sul- 
phates, phosphates, etc.) and of residual silicates and oxides 
(kaolin, quartz, ferric oxides, etc.). Neglecting the minor trans- 
formations which do not concern us here, the operation may be 
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