222. Professor J. Joly—The Age of the Earth. 



acid in the primitive atmosphere must be supposed to act upon the 

 primitive rock much as it would in the laboratory experiment of 

 to-day, when we put such rock to digest in the aqueous solution of 

 the acid. Taking, then, HCl as probably by far the most abundant 

 of the free active acids of the primeval atmosphere, the outcome 

 of the chemical reaction between the acid and the average rock-crust 

 affords such a mass of sodium as would shorten Geological Time by 

 some six million years. (The corrigenda affixed to my paper should 

 be consulted in reference to this number.) 



I may add with regard to vague ideas (not unprevalent) as to 

 long ages of boiling waters acting upon the primitive rocks that 

 calculation relegates these long ages to their proper importance. 

 In fact, the rate of cooling of lava after solidification is so rapid that 

 the long ages shrink to a very few years. " The thickness of the 

 wholly solidified crust grows at first with extreme rapidity — at the 

 •end of a year it may be as much as ten metres, with a surface almost 

 or quite cool enough for some kinds of vegetation." (Lord Kelvin, 

 " The Age of the Earth " : Address to the Victoria Institute, 1897.) 

 The subsequent rate of cooling may be inferred from a further 

 extract from the same address : " To fix our ideas let us suppose 

 at the end of one year the surface to be 80° (Cent.) warmer than 

 it would be with no underground heat, then at the end of 100 years 

 it would be 8° warmer, and at the end of 10,000 years it would be 

 0-8 of a degree wai-mer." So then (and, be it observed, these figures 

 are independent of what we postulate as to the gross thermal actions 

 involved in earth-cooling) the long ages shrink to a period of 

 a centuiy, during which the water fell through its critical point 

 to a liquid resting on our earth, warmed about 8° above what it 

 is to-day; if, indeed, a lesser sun-heat (see Professor Perry's article 

 in Nature, vol. Ix, p. 247) did not act to make it considerably cooler. 

 Now if we assume that the mean rate of solvent and chemical 

 aqueous denudation during this period was as much as one hundred 

 times as great as to-day, we find 10,000 years' work accomplished 

 in the first 100 years : involving a correction evidently quite 

 negligeable. 



But difficulties which may be described as based on highly 

 probable speculation are not the only ones which have to be faced 

 by the advocates of the primitive alkali-charged ocean. Let us 

 suppose they have surmounted the difficulties of accounting for the 

 state of things they desire to establish. They have now to explain 

 how the Jmoicn enormous subsequent formation of sediments was 

 effected from the original rock-crust without putting into the ocean 

 the bulk of the alkalies they have already assumed to be in it. Still 

 more, they have to explain the coincidence that the approximate 

 measure of the sodium missing from these sediments very closely 

 suffices to account (the error being on the side of excess) for the 

 amount of sodium in the ocean. This is a point resting on estimates 

 certainly sufficiently reliable for the degree of accuracy required 

 in confirmatory evidence, and can neither be slighted nor ignored 

 till its fallacy is demonstrated. 



mM 



