682 LT. €. CHAMBERIGDN 
by experienced glacialists, and their concurrent judgment is that 
the least of the notable interglacial intervals was at least two or 
three times as great as the postglacial interval. It would not be 
exceeding current judgment, therefore, to assign from 80,000 to 
120,000 years as the duration of a typical interglacial epoch. 
But in the interest of conservatism let the postglacial interval 
be taken at 10,000 years and the interglacial at 20,000 or 30,000 
years. Whisseems to) me excessively (‘consenvative: sy ligthe 
assigned agencies can affect a reénrichment of the atmosphere 
in carbon dioxide to an amount somewhat exceeding the present 
content and then again a depletion of one half within 20,000 or 
30,000 years, the hypothesis will not be excluded by time 
limitations. 
We have the following pertinent data based in part on 
Reade’s' estimates of the present rate of removal of carbonates: 
Total mass of the atmosphere - - - - - 5X 10% tons 
Mass of atmospheric CO, (reckoned by weight at .0006) - 3X 10” tons 
Total mass of CO, taken annually from the atmosphere - 162X107 tons - 
Mass of CO, consumed annually in original carbonation 
(reckoned by area at 20 per cent. of the land) — - - 27X107 tons 
If reduced one half on account of the slower rate of 
decomposition of crystallines it will be 13.5107 
tons, in which case the other half is to be added to 
the following item, if Reade’s estimates are correct.) 
Mass of CO, consumed annually in forming bicarbonates - 135X107 tons 
Time required at this rate to consume total atmospheric 
CO,, assuming no return” - - - - - - 1852 years 
Time required at this rate, without return, to consume 
one half atmospheric CO, (the reduction requisite 
for glaciation.) - - - - - - - - g26 years 
Time required to consume half the ‘free’ and “loose” 
CO, of the ocean (estimated at 18 times that of the 
atmosphere) without return - - - - - 16,668 years 
Time required to consume half the CO, of the atmos- 
phere and the ocean combined, without return - - 17,594 years 
The last items which involve the reduction of the carbon 
dioxide in the ocean as well as in the atmosphere are not really 
tLoc cit. on p. 569. 
