WIV ROTMESISIOPACAU SE OF GLACIAL PERIODS 569 
equivalent of carbonic acid to render them bicarbonates, and 
this second equivalent is derived essentially from the atmosphere. 
There is herein a source of temporary loss, temporary because 
the second equivalent of carbon dioxide remains associated with 
the bases in the sea only until deposition takes place, when it is 
set free. It is to be noted that a second equivalent is also taken 
up in the formation of original carbonates if they are dissolved. 
As the crystalline rocks occupy only a little more than 20 per 
cent. of the land surface and are probably not removed as fast 
as the secondary rocks, not more than about one fifth, probably 
not more than one tenth, of the bicarbonating carbon dioxide is 
associated with original carbonation. The remaining four fifths 
or more are occupied in bicarbonating and dissolving the calca- 
reous and magnesian portions of the secondary rocks. It follows 
that the ratio of carbon dioxide now taken out of the atmosphere 
as second equivalent in any unit of time, to that taken out as 
first equivalent, is probably fully five to one, and not unlikely as 
high as ten to one. This ratio would not necessarily hold for 
past periods, but in all those under consideration the second 
equivalent was undoubtedly very much greater than the first. 
Accepting, for the purposes of a rude estimate, the data of T. 
Mellard Reade,’ the amount of carbon dioxide removed annually 
by original carbonation, reckoned by proportional area, is 270 
million tons, the amount temporarily removed as the second 
equivalent of the bicarbonates is 1350 million tons ; the amount 
. simply transferred from the land to the sea as the first equivalent 
of the carbonates previously formed is 1080 million tons; the 
total mass taken from the atmosphere annually being therefore 
1620 million tons, and the total mass removed to the sea 2700 
million tons. Besides uncertainties in the original estimate of 
Reade, the first item is subject to correction (probably large) for 
the slower rate of disintegration of the crystalline rocks. This 
is, however, somewhat offset by weathering action on the sili- 
cates that remain undecomposed in the secondary rocks, and on 
t Addresses, Geol. Soc. of Liverpool, 1876 and 1884, quoted in Dana’s Manual, 
p. 191. 
