400 Mr. J. Stevenson on the Chemical and 



partly by animal nutrition and respiration, partly by rapid 

 combustion in fires, and very largely by eremacausis, or slow 

 oxidation and decay under the influence of air and moisture. 

 The proportion that escapes oxidation through being deposited 

 under fairly aseptic conditions, as in peat bogs, or by being 

 swept out to sea and deposited along with other matters 

 beyond the reach of atmospheric oxygen, is relatively very 

 small. We have no data to guide us as to its total amount, 

 but if we call it 25,000,000 tons annually — this being, as we 

 have seen, the quantity of coal that would have to be deposited 

 annually to give us 500,000,000,000,000 tons in 20,000,000 

 years — the proportion of vegetable remains preserved in the 

 form of coal would be equal to about the g-j-g part of the total 

 carbon separated from the atmosphere annually by vegeta- 

 tion. Again, if we call the annual production of coal 740,000 

 tons (the amount that would give us 500,000,000,000,000 

 tons in 680,000,000 years), we should have the ^mb P ar ^ °^ 

 the carbon separated by vegetation permanently preserved in 

 the form of coal. Of these figures the Litter (jy^j) seems 

 credible enough ; and if the former (519) should seem to be 

 rather high for modern times, it is by no means incredible 

 when taken as an average for the whole of geological history. 

 For if there was no free oxygen in the earth's primitive 

 atmosphere, and we may fairly enough say that by hypothesis 

 there must have been none if on the average 25,000,000 tons 

 of coal have been annually deposited and permanently pre- 

 served for the last 20,000,000 years, then there could at first be 

 no eremacausis or other oxidation of vegetable remains due to 

 atmospheric oxygen ; and therefore those who hold that there 

 was no primitive free oxygen may confidently say that a much 

 larger proportion of vegetable remains could be preserved then 

 in the form of coal than is possible at the present day. Even 

 without going so far as to postulate that there was no free 

 oxygen, but simply by making the probable assumption that the 

 percentage of free oxygen in the atmosphere was considerably 

 less than it is now, and that the percentage of carbonic acid was 

 considerably greater than it is now, it could be maintained 

 that eremacausis and other modes of atmospheric oxidation 

 were in all probability much less active than they are now, 

 and therefore that a larger proportion of vegetable remains 

 would be preserved as coal than is now possible. We may 

 therefore conclude that though this line of inquiry, like our 

 previous ones, does not give exact and definite results, it at 

 least puts no serious difficulty in the way of making a high 

 estimate of the world's supply of coal. 



Our efforts so far have been directed specially to the object 



