656 He (Oz Cle VANIIESBISSEI ENS 
dioxide. The delay in the appearance of land life is sufficiently 
assignable to the obstacles to its evolution to make needless a 
theoretical appeal to a noxious condition of the atmosphere. 
But if we compute the amount of carbon which has been 
extracted from the atmosphere in the production of the carbon- 
ates and the carbonaceous deposits, and restore this to the 
atmosphere, following a time-honored custom, we are led to the 
time-honored conception of an exceedingly extensive, dense, 
warm and moist atmosphere. The amount of carbon dioxide 
represented by the limestones and carbonaceous deposits has 
been variously estimated at twelve thousand to one hundred and 
fifty thousand times the present content of the atmosphere. My 
own estimates lead me to favor figures lying between twenty 
thousand and thirty thousand. These estimates do not go back of 
the Palaeozoic series and leave an unknown factor to be added for 
the pre-Cambrian limestones and carbonaceous deposits. The 
amount of carbon extracted from the atmosphere since the 
introduction of air-breathing life is probably not less than 8000 
or 10,000 times the amount now in the air. This forces the 
question whether this large amount of carbon dioxide or any 
major part of it was ever in the atmosphere at any one time. 
The alternative is to assume that the atmosphere was origi- 
nally less ample and has been fed as well as robbed during all 
the geological ages, its history being a struggle between enrich- 
ment and depletion. In some measure this is an accepted view, 
but it is part of the purpose of this paper to show that the way 
is open to freer hypothesis in this direction. 
The current view of a vast original atmosphere is derived 
less perhaps from the computation of material extracted from it 
than from theoretical views regarding the origin and early history 
of the earth. There has been quite general assent to the nebu- 
lar theory of the origin of the earth. Even where dissent from 
the gaseous features of this theory has been entertained there 
has been acquiescence in the doctrine of the earth’s early molten 
condition and all that it implies. If the earth were in a thor- 
oughly molten condition, there would seem at first thought but 
