ABUNDANCE OP THE CHEMICAL ELEMENTS. 135 
A. B. C. D. E. F. G. H. 
Si0 2 _ 61-89 61-89 60-49 60-66 60-50 59-80 56-75 58-59 
A1 2 0 3 _ 15-71 15-73 16 08 15-46 14-30 14-65 14-90 1504 
Fe 2 0 3 _ 1-81 3-18 2-47 2-74 3-35 4-99 4-58 3-94 
PeO ___ 3-65 2-40 2-86 2-27 4-31 2-92 3-71 3-48 
CaO _ 4-51 4-58 6-15 4*71 3-52 5-19 5 79 5-29 
MgO _ 2-40 3-08 4-31 3-35 500 3-45 5-22 4-49 
K 2 0_ 3-54 2-70 1-80 3-97 2-52 3-06 2-90 2-90 
Na 2 0_ 3-28 3-70 3-31 3-54 2-49 2-98 3-24 3-20 
H 3 0_ 1-69 1-59 1-12 -97 2-53 2 09 2-12 1-96 
98-48 98-85 98 59 97-67 98-52 99-13 99-21 98-89 
That these means are remarkably concordant, especially as 
regards the columns A to F, is at once evident; but a reduc¬ 
tion to elementary form renders the agreement even more 
striking. 
A. B. C. D. E. F. G. H. 
Si_ 28-88 28-88 28-23 28-31 28-23 27-91 26-50 27-34 
A1_ 8-31 8-32 8-51 8-18 7-57 7-75 7-89 7-96 
Fe_ 4-11 4-09 3-96 3-68 5-71 5-77 6-09 5-47 
Ca_ 3-22 3 27 4-39 3-37 2-51 3-71 4-13 3-78 
Mg _ 1-44 1-85 2-58 2-01 3 00 2-07 3-13 2-69 
K_ 2-94 2-24 1-49 3-29 2-09 2-54 2-41 2-41 
Na_ 2-43 2-74 2-46 2-63 1-85 2-21 2-56 2-37 
H_ -19 -18 -12 -11 -28 -23 -24 -22 
O_ 46-96 47-28 46-85 46-09 47-28 46-94 46-26 46-65 
98-48 98-85 98-59 97-67 98-52 99-13 99-21 98-89 
The thesis that the crust of the earth is fairly homogene¬ 
ous in composition is thus sustained by positive evidence. 
The variations in the foregoing table are as small as could 
reasonably be expected. 
So far, however, only nine of the rock-forming elements 
are accounted for. The proportions of the others are less 
easily computable, although in some cases fair estimates can 
be made. In certain directions very many of the analyses 
considered, especially in the columns A and G, were incom¬ 
plete, constituents like titanium, manganese, phosphorus, 
etc., having been ignored as not essential to the purpose of 
the analyst. These substances appear in part, therefore, as 
