292 ATMOSPHERIC FACTOR IN EVOLUTION. 



evenly distributed over the entire area of Great Britain and Ireland 

 what would be the thickness of the resulting seam? The area of 

 Great Britain and Ireland is 120,832 square miles = 120,832 x 5,280 

 X 5,280 square feet. Now one entire cubic ft. of coal weighs 

 about 80 lbs. Therefore the weight of a uniform seam of coal one 

 foot in thickness, spread throughout Great Britain and Ireland, 

 would weigh 120,832 x 5,280 x 5,280 x Solb. 



But the estimated existing coal on the same area is nearly 

 200,000,000,000 X 20 x 4 X 28 lb. If we divide this long number of 

 pounds by the former number of pounds, we get as a result if 

 approximately. That is, if the total coal estimated as existing in 

 Great Britain and Ireland were evenly distributed it would form a 

 seam of about if ft. in thickness. This result is a wonderfully near 

 approach to the result of our previous calculations. The result 

 of these two calculations is this : — that supposing we take Great 

 Britain and Ireland and shut them and their atmosphere off from 

 the rest of the world and returned its buried carbon or coal 

 back to the air in the form of carbon dioxide, the amount of 

 carbon dioxide so returned would be just about 500 times the 

 quantity of carbon dioxide in the atmosphere at the present time. 



It may, however, be urged that Great Britain and Ireland 

 have more than their share of the coal of the world ; but on the 

 contrary, it may be urged that many coal-fields have yet to be 

 discovered. Japan has seams of coal 14 to 20 or more feet 

 in thickness being worked, while in Manchuria, coal looft. thick 

 is reported. But what of the coal under the seas and lakes? 

 It was under water that the process of coal formation took place. 

 To return, again, to the estimate of the total amount of coal in 

 Great Britain and Ireland. The amount already given was only 

 that of all coal over ift. in tlhickness. There must be large 

 quantities of coal in seams under ift. thick. But besides coals 

 we have other substances in the crust of the earth formed from 

 plants, that is, from the carbon of the original atmosphere. We 

 have peat, lignite, bituminous shale, etc. Then we have 

 more or less carbon scattered throughout the other rocks of the 

 earth's crust. Besides, we must not forget the carbon in the 

 various Carbonates in the various strata of the earth. 



I think, then, that we have good reason for believing that at 

 the beginning there must have been a very considerable quantity 

 of carbon dioxide in the air, of which most of the carbon is now 

 buried in the earth, and of which the oxygen is now partly free 

 in the air and partly buried combined as oxides. 



Suppose every atom of carbon in the air at the present time 

 were converted into coal, how much would it make? As there 

 is now only ^-^ of the amount of carbon dioxide assumed in 

 my first calculation, the result must be sSo part of the first 

 result, that is, of if feet = about ~r of an inch. Therefore 



the seam of coal formed by all the carbon in the air at the 

 present time would be about ^ of an inch in thickness. We 



thus see that, at the beginning there must have been a large 

 quantity of carbon dioxide and very little oxygen in the air. 



(2) Next let us look at the present time. The proportions of 

 oxygen and carbon dioxide in the air at the present time are 



