1892.] NATURAL SCIENCES OF PHILADELPHIA. 91 



follow the return to the atmosphere of the carbonaceous constitu- 

 ents of all accessible coal now and for ages past safely contained in 

 the storehouse of the earth. The composition and weight of the 

 existing atmosphere as well as of coal being well known, the first 

 step necessary for such a calculation is to get a world-wide esti- 

 mate of the quantity of such accessible coal. 



Sir Charles Lyell and the early geologists at first supposed that 

 the enormous geological destructions and reconstructions of which 

 they observed the evidences everywhere on the land surfaces of the 

 globe, had equally affected all surfiices, involving the subsidence of 

 continents and the corresponding elevation of sea bottoms, in 

 short a wide and perhaps universal and repeated interchange of 

 continental and oceanic areas. But it has now long been known 

 and in fact proved by the researches of the Challenger expedition 

 and other investigations, that those early views were erroneous, and 

 that notwithstanding the repeated changes of height and level 

 everywhere and at all times prevailing over and throughout all 

 land surfaces, the existing proportions between land and ocean 

 areas have in the main always been maintained at least outside the 

 depth line of 1000 fiithoms. The evidence of this important fact is 

 abundant and conclusive, but as it has recently. been lucidly summed 

 up in the latest work of Mr. A. R. Wallace,* it need not be repeated 

 here. 



Accepting these better modern views, it is clear that under the 

 main portions of the ocean, neither derivative rocks nor fossil vege- 

 tation are to be looked for, and cannot exist in appreciable quan- 

 tity. But the area of the entire land surface of the earth with its 

 included waters, bears to the entire oceanic area the proportion of 

 28 to 72, according to the careful computations of Mr. John 

 Murray, cited and approved by Wallace, a proportion which, as 

 shoAvn by Mr. Wallace's map of the 1000 fathom line, would not be 

 materially modified if the littoral portion of the sea bottom lying 

 inside that line should be tranferred from the oceanic to the land 

 area. 



Now since, as before observed, we possess accurate knowledge 

 both of the constituency of the atmosphere as now existing, and 

 also its weight both as a whole and per square foot of the earth's 

 surface, we only require to know the quantity of coal existing on 28 

 per cent, of the earth's surface to compute the quantity of carbon 



* Darwinism, pp. 341-349. 



