NOVEMBEB 20, 1008] 



SCIENCE 



703 



was undoubtedly a very rapidly formed 

 deposit, exhibits a radio-activity quite com- 

 parable with that of the Globigerma oozes, 

 deposits which it most nearly resembles. 

 In this deposit, clearly, the uranium must 

 have collected along with the calcareous 

 materials. We can with security argue 

 that the similar oozes collected to-day must 

 likewise contain uranium. In the case of 

 the red clays we have the direct determina- 

 tion of the uranium which Professor Emil 

 Werner was so good as to make at my re- 

 quest. Considering the difficulties attend- 

 ing its separation, the result must be taken 

 as supporting the view that here, too, the 

 radium is removed from the uranium. Re- 

 garding the eiforts of other observers to de- 

 tect uranium in such deposits, it is note- 

 worthy that without the guidance of the 

 radium, enabling specially rich materials to 

 be selected for analysis, the success of the 

 investigation must have been doubtful. 

 The material used was a red clay with the 

 relatively large quantity of 54.4 billionths 

 of a gram per gram. In a few grams of 

 this Werner obtained up to seven twelfths 

 of the total theoretic amount, and of course 

 the separation 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 

 sub-oceanic 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 consider- 

 able security. As a major limit I believe 

 the estimate of the total mass of deposit is 

 unassailable, and such deductions as might 

 be applied will still leave it an approxima- 

 tion 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 oeean.^ 

 These are the salts of sodiimi. 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 incep- 

 tion of the oceans. Some years ago I de- 

 duced on this basis that the igneous rocks 

 which are parent to the sodium in the sea 

 must have amounted to about 91 X 10^® 

 tons.^ This figure in no way involves the 

 rate of supply by the rivers, or our estimate 

 of geological time. It only involves tKe 

 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 sedi- 

 mentary rocks— a factor also fairly well 

 known. Mr. F. W. Clark, to whom geo- 

 logical 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 

 84.3 X 10® cubic miles.^ On a specific 

 gravity of 2.6 my estimate in tons gives 

 nearly the same result : 84 X 10" 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 myself of Van Hise's and 

 Clark's estimates of the total amount of the 

 sedimentaries and the fraction of these 

 which are calcareous ),° and, allowing for 



'Trans. Royal Dublin Soc, Vol. VII., Ser. II., 

 pp. 23 ff. 



^ Ibid., p. 46. 



' " The Data of Geochemistry," by F. W. Clark, 

 p. 29. 



'Ibid., p. 31. 



