1906] 



IN CHEMICAL GEOLOGY. 



25 



4.79 per cent, of lime. This would form 8.55 per cent, of calcium 

 carbonate, or 11. 2 per cent, of the average limestone. But at least 

 half of the lime has remained in the other sediments, so that its true 

 proportion can not reach 6 per cent., or one third the proportion of 

 the sandstones. The remainder of the igneous material, plus some 

 water and minus oceanic sodium, has formed the siliceous residues 

 which are grouped under the vague title of shale. Broadly, then, 

 we may estimate that the lithosphere, within the limits assumed in 

 this memoir, contains 95 per cent, of igneous rock, with 5 per cent, 

 of sedimentaries. If we assign 4.0 per cent, to the shales, 0.75 per 

 cent, to the sandstones, and 0.25 per cent, to the limestones, we shall 

 come as near to the truth as is possible with the present data.^ On 

 this basis, the average composition of the lithosphere may be summed 

 up as follows. The analyses of the sedimentary rocks are recal- 

 culated to 100 per cent. : 



95 Per Cent. 

 Igneous. 



SiOo 59.87 



A1203 15.02 



Fe,03 2.58 



FeO 3.40 



MgO 4.06 



CaO 4.79 



NaoO 3.39 



K,0 2.93 



H.O 1.86 



TiOo -2 



ZrOo 03 



CO, 52 



P.O5 26 



S II 



SO3 



CI 07 



F .02 



BaO II 



SrO .04 



MnO 10 



NiO 03 



CroOa 05 



V,03 03 



LioO 01 



C 



4 Per Cent. 



Shale 



58.10 



15.40 



4.02 



2.45 

 2.44 



3. II 

 1.30 



3-24 

 5-00 



.65 



.17 

 .64 



.05 



0.75 Per Cent. 

 Sandstone 



78.33 

 4.77 

 1.07 



.30 

 1. 16 

 S.50 



.45 

 I.31 

 1.63 



.25 



5-03 

 .08 



.07 



05 



.80 



0.25 Per Cent. 

 Limestone. 



5-19 

 .81 



•54 



7.89 



42.57 



.05 



.33 



•n 

 .06 



41-54 

 .04 

 .09 



.05 

 .02 



.05 



Average. 



59-79 

 14.92 



2.e2> 



Z-ZZ 



3-98 



4.82 



3-28 



2.96 



1.98 



•71 



.03 



•74 



-25 



.10 



.02 



-07 

 .02 



.10 

 .04 

 .09 

 .03 

 -05 

 .02 

 .01 

 •03 



100.00 



100.00 



^ Van Hise, " A Treatise on Metamorphism," U. S. G. S. Monograph 47, p. 940, 

 divides the sedimentary rocks into 65 per cent, shales, including all pelites and 

 psephites, 30 per cent, sandstones, and 5 per cent, limestones. 



