570 T. 6. CHAMBERLIN, 
the late volcanics which are not all included in the 20 per cent. 
of the land area reckoned as crystalline. The second item is sub- 
ject to correction to the extent that the salts were normal car- 
bonates and not bicarbonates. 
Reciprocal sources of temporary gain—The second equivalent 
of the carbonates in the ocean is subject to easy removal under 
suitable conditions, and reénriches the atmosphere by diffusion 
into it from the ocean. The conditions under which this is set 
free are of critical importance to our hypothesis. We have to 
consider (a) saturation, (6) chemical reactions and dissociations, 
and (c) organic action. 
a. Absence of general saturation—In the absence of other 
agencies of removal the accumulation of calcium bicarbonates in 
the ocean would go forward to the point of saturation, if there 
were a sufficient amount producible. It would then be depos- 
ited as limestone, and the second equivalent of the carbon diox- 
ide would be set free. There is little reason to think, however, 
that general saturation has been reached during the known por- 
tion of the earth’s history. In local basins subject to peculiar 
conditions, saturation certainly has been attained, as the marls 
of the great saliferous deposits testify. The present approach 
to oceanic saturation in calcium carbonate is apparently only 
about 40 per cent. If the ocean in former times had reached 
saturation in calcium carbonate and any notable precipitation 
had followed, the precipitate should appear as a distinctive con- 
stituent of the clastic deposits. While calcareous matter which - 
might be so interpreted occurs in some of these deposits, there is 
a notable absence of anything of the kind in many others where it 
might be expected, and the general character of the sandstones 
and shales seems more concordant with the accepted view that 
they were laid down in waters that did not, except in special 
cases, directly deposit calcareous matter. In view of the proba- 
ble presence of lime-secreting organisms, the problem is gener- 
ally rather to account for the paucity of calcareous matter than 
its abundance in the clastic deposits. The explanation is doubt- 
less found in the undersaturation of the sea water and its ability 
