ON COAL. 139 



that all the carbon was preserved. This is in the highest degree im- 

 probable, not to say impossible. Probably much more than half was 

 returned to atmosphere in the form of carbonic acid and carburetted 

 hydrogen. Again, we have taken no account of the enormous periods 

 of time during which there was no carbon deposited on the spot in 

 question, and represented by the intervening strata of limestone, 

 sandstone, and shale. The estimate we have given above, therefore, 

 probably falls very far short of the truth. Let us try another. 



According to Messrs. Lyell and Dawson the coal strata of Nova 

 Scotia are about three miles in thickness at the South Joggins. At 

 another point, nearly 100 miles distant, (Albion mines,) they found 

 the thickness nearly the same. There is little danger, therefore, of 

 erring on the side of excess, if we take the average thickness of the 

 strata over the whole basin at one and a half miles. Now, the area 

 of this coal field, according to Mr. Lyell, is about 3,600 square miles. 

 This would give, as the solid contents of these strata, 54,000 cubic 

 miles. But we have already seen that this enormous amount of mat- 

 ter was almost certainly accumulated at the mouth of a great river. 

 Let us see how long it would take one of our great rivers to do the 

 work. I shall select for this purpose the Mississippi and the Ganges, 

 because they are both very large rivers, carrying vast amounts of 

 sediment, and because accurate observations have been made as to the 

 amount of sediment brought down by them. These observations have 

 been made upon the Mississippi by Drs. Forshay and Reddell, of New 

 Orleans, and by Captain Strachey, British engineer, upon the Ganges. 

 According to these observations it would take the Mississippi 2,000,000 

 years, and the Ganges* 3*75,000 years to perform the work. And yet 

 the period we are now discussing is probably not one-thirtieth, cer- 

 tainly but a small portion of the entire geological history of the earth. 



It will no doubt be objected to this estimate that it is founded upon 

 a particular theory, and this theory may be incorrect, and the estimate 

 thus falls to the ground. In answer to this objection it is only neces- 

 sary to state that we are acquainted with no other circumstances under 

 which strata accumulate so rapidly as at the mouths of rivers. Any 

 other conceivable theory, therefore, would only increase the time. 



Again, it will probably be objected that the agencies of nature may 

 have been and probably were more active in earlier periods of the his- 

 tory of the earth than now. Such a notion, although almost universal 

 among intelligent people and very prevalent even among geologists, 

 is, as it seems to me, utterly without foundation in reason. In refer- 

 ence to this point geologists may be divided into two classes. The 

 first and most numei'ous class hold that the agencies of nature have 

 gradually decreased in activity from the earliest times until now. The 

 other, to which Mr. Lyell and his followers belong, believes that these 

 agencies have acted much as they do now through all time ; that there 

 has been no progressive change of any kind, neither in the earth nor 

 its inhabitants. Now, it seems to me that it can be proved, or at 



* This amaziiiff difference in favor of a smaller river is due to the fact that the Ganges, 

 being- a tropical river, the rains all i'all during six months, and are therefore very heavy. The 

 washing of the soil and resulting sediment are necessarily in proportion. The mountainous 

 country in which the Ganges takes its rise contributes also to the same result. 



