702 Prof. J. Joly on the Radioactivity of 



matter of surmise. Most indications of deep-seated high 

 temperatures are restricted to the geosynclines and over 

 these sediment-laden areas the surface crust cannot be con- 

 sidered normal. 



The Secondary Mocks. 



The radium content of the secondary rocks has been dealt 

 with by A. L. Fletcher*, using the method by fusion as it is 

 applied in my laboratory. The results are : — 



For 24 arenaceous rocks 1*5 



„ 9 altered ditto 1*5 



,, 16 argillaceous rocks 1*3 



,, 9 schistose „ 1*] 



,, 24 calcareous ,, 0*8 



These rocks were treated in detail, the figures are the mean 

 of the several observations in each group. The fact that the 

 argillaceous rocks are inferior in radium content to the 

 arenaceous is to be explained in the nature of the arenaceous 

 materials dealt with. Many of these were by no means 

 ultimate products of solvent denudation, that is were not 

 purely quartzose. The importance of verifying the means 

 for the two leading groups led me to treat composite sediments 

 in the electric furnace. The agreement with the means given 

 above is satisfactory: — 



For 39 sandstones, conglomerates, and coarse grits 1*5 



11 



20 slates and shales 1*5 



It would appear from the comparison of the above with 

 the few published results on sedimentary rocks obtained by 

 the solution method that most of the latter are too low by 

 about 50 per cent, of their value. The leading data known 

 to me are : — 



Struttf on 8 slates, sandstones, and clays 1*2 



„ on 8 calcareous rocks 1"0 



Eve & MclntoshJ on 5 clays and limestones 0\59 



„ „ on 8 limestones, sands, & clays 1*02 



Farr & Florance§ on 2 calcareous rocks 0'37 



Biichner || on 1 1 calcareous rocks 1'4 



* Phil. Mag. Feb. 1912. 



t Strutt, Proc. R. S. lxxviii. A. p. 150. 



X Eve & Mcintosh, Phil. Mag. Aug. 1907 ; and Trans. R. S. Canada, 

 3rd ser. 1910, vol. iv. p. 69. 



§ Farr & Florance, Phil. Mag. Nov. 1909. 



II Biichner, Konink. Akad, van Wetensch. te Amsterdam. Proc. Feb. 

 1911. 



