78 
form of coal, petroleum, natural gases, etc.—some of the hydro- 
carbons may have an inorganic origin. 
Source of temporary loss of COz2: (1) The locking up of 
CO2 as bicarbonates in the solution of the limestones and the dolo- 
mites. T. M. Reade estimates that this is annually 1350 million 
tons as compared with 270 million tons in original carbonation. 
(2) Absorption in sea water. (3) Some CO2 may be used in 
decomposing sulfates by organisms. | 
Sources of permanent gain: (1) The CO2 inclosed in the 
crystalline igneous rocks set free by disintegration, (2) that 
brought up by volcanoes, (3) possibly some brought in by mete- 
orites. | 
Sources of temporary gain: (1) chemical action—the set- 
ting free of the second CO2 in the bicarbonates by the action of 
organisms, (2) by dissociations, (3) by setting free or diffu- 
sion into the air of the CO2 in the sea water due to a rising tem- 
perature and (4) by the decomposition of organic matter. 
These fluctuations of carbonic acid are correlated with the 
elevation and extension of the land on the one hand and the ad- 
vance of the sea on the other. During extensive land elevation 
the silicates are changed to carbonates more rapidly and the dis- 
solved limestones carried to the sea more rapidly, both processes 
using up CO2 from the atmosphere. Correlated with this is a 
lessening of the sea area, particularly of the continental shelf 
which is the habitat of the lime-secreting forms. Limitation of 
the lime-secreting forms retards the process of freeing the CO2. 
The result is a reduction in temperature which increase the capac- 
ity of the sea for holding CO2. 
In periods of sea extension and land reduction the shallow 
water area is increased giving acceleration to the agencies that set 
CO2 free from the ocean, at the same time the land area being 
diminished the carbonation of the silicates would go on more 
slowly as likewise the solution of the limestone thus acting con- 
jointly to increase the CO2 in the atmosphere. 
APPLICATION. To apply the hypothesis to our last glacial 
period is the next step. It is noted that there was a marked ele- 
vation and extension of the land at or near the close of the Plio- 
