1892.] NATURAL SCIENCES OF PHILADELPHIA. 93 



from it and now fixed in such cai-bonates as limestones, marbles, 

 chalks and corals, cannot be looked for without the recurrence of 

 such intense heat as there is no longer reason to expect, while on 

 the contrary, the secular diminution of both solar and internal heat 

 must tend to increase rather than diminish the stability of those 

 compounds. 



But the lower horizontal lines of the table, or some condition 

 intermediate between them, approximate so nearly to the actual 

 quantity of existing and available carbon accumulations assumed 

 in column VI, that on the entire combustion of such accumulations 

 nothing less can be looked for than the atmospheric modifications 

 indicated in the preceding columns. The last line for instance, 

 shows that assuming all the mineable coal of the earth to equal one 

 stratum of "SoTl of one inch uniform thickness covering the entire 

 land surface (this being taken at 28 per cent, of the Avhole) its com- 

 bustion would abstract one per cent, from the existing twenty-three 

 per cent, of all atmospheric oxygen and add 'SIB of one per cent, 

 of its present weight to the atmosphere in carbon dioxide. 



We are not Avithout means of verifying to some extent this 

 assumed thickness of the supposed universal stratum of carbon. In 

 North America we have seen that the total computed quantity 

 available is 673,013 million tons, a quantity which, if equally 

 diff'used over the North American continental area of 7,400,000 

 square miles, would give a uniform thickness of *924 of one inch. 

 Since the conditions of the carboniferous period have at one time or 

 other been common throughout all parts of the land surface of the 

 globe as proved by the universal diflfusion under similar conditions 

 of coal or fossil vegetation, it would not seem a violent assumption 

 to suppose that when we shall be as well acquainted with the other 

 parts of the world as we now are with North America, it will be 

 found that coal is not on the whole very unequally distributed, and 

 that the tolerably well ascertained fact of the equivalent stratum 

 for North America approximating an inch in thickness, will not be 

 found materially different in other parts of the earth's land surface, 

 and may at least be taken at "8371 of an inch as indicated in the 

 lowest line of the tabular statement, with all the other facts stated 

 in the same line as appurtenant. 



But just as the original abstraction of carbonic acid from the air 

 by the carboniferous vegetation has certainly once modified to some 

 extent or other all then existing life and rendered possible the 



