UEANIUM AND GEOLOGY JOLY, 363 



gram per gram. In a few grams of this Werner obtained up to 

 seven-twelfths of the total theoretic amount, and of course the sepa- 

 ration of the uranium is not likely to have been complete. 



It might be thought a hopeless task to offer any estimate of the 

 total bulk of the suboceanic deposits and from this to arrive at some 

 idea of the quantity of radium therein contained. Nevertheless, such 

 an estimate is not only possible, but is based on deductions which 

 possess considerable securit}'. As a major limit I believe the estimate 

 of the total mass of deposit is unassailable, and such subtractive cor- 

 rections as might be applied will still leave it an approximation to the 

 truth. 



The elements of the problem are simple enough ; we know that the 

 sedimentary rocks have been derived from the igneous, some 30 per 

 cent of the latter entering into solution in the process of conversion. 

 Some of the soluble constituents, owing to their great solubility, have 

 remained in solution since they entered the ocean." These are the 

 salts of sodium. An estimate of the amount of these salts in the 

 ocean gives us a clue to the total amount of rock substance which has 

 contributed to oceanic salts and oceanic deposits since the inception 

 of the oceans. Some years ago I deduced on this basis that the 

 igneous rocks which are parent to the sodium in the sea must have 

 amounted to about 91X10^'' tons.^ This figure in no way involves 

 the rate of supply by the rivers or our estimate of geological time. 

 It only involves the quantity of sodium now in the ocean — a fairly 

 well known factor — and the loss of this element, which occurs when 

 average igneous rocks are degraded into sedimentar}^ rocks— a factor 

 also fairly well known. ^Mr. F. W. Clarke, to whom geological science 

 is indebted for so much exact investigation, has recently repeated 

 this calculation, using data deduced anew by himself, and arrives at 

 the result that the bulk of the parent igneous rock was 84.3X10° 

 cubic miles.*^ On a specific gravity of 2.6 my estimate in tons gives 

 nearly the same result — 84X10'^ cubic miles. 



Now, about one-third part of this parent rock goes into solution 

 when breaking up into a detrital sediment. The limestones upon the 

 land are part of what was once so brought into solution. Having 

 made deduction of these former marine deposits (and I here avail my- 

 self of Van Hise's and Clarke's estimates of the total amount of the 

 sedimentaries and the fraction of these which are calcareous) f and 

 allowing for the quantity remaining in solution in the ocean, the result 

 leaves us with the approximation of 20,000,000 cubic miles of matter 

 once in solution and now for the greater part existing as precipitated 



° Trans. Royal Dubliu Soc, Vol. VII, ser. 2, p. 23 et seq. 

 & Ibid., p. 46. 



c The Data of Geochemistry, by F. W. Clarke, p. 29. 

 <* Ibid., p. 31. 



