200 Scientific Intelligence. 



2. Meteorites vs. The Earth ; by Oliver C. Farringtox. 

 (Communicated.) — The criticism by Merrill* of the writer's com- 

 parison of the composition of meteorites and the earth suggests to 

 the writer some further observations. With Merrill's view, that 

 the average compiled by him, by omitting the metallic iron and 

 associated metals and sulphides from the sum of meteorite compo- 

 sitions, is "the most acid phase conceivable" for a meteoritic 

 magma, the writer can hardly agree. 



The quantity of unknown matter of the earth so greatly ex- 

 ceeds that of the known, that in comparing meteorites with 

 the known matter of the earth only a few meteorites need 

 be taken. Assuming a knowledge of the composition of the earth 

 to a depth of ten miles,f and regarding the mean diameter of the 

 earth as 7913 miles, the unknown substance of the earth exceeds 

 the known in the ratio of 131:1. Hence only 4 of the analyses, 

 numbering 443 in all, which were used by the writer to obtain 

 an expression for the composition of the earth, \ need be used 

 to represent the composition of the earth's crust. Such a sum, 

 moreover, would have the advantage of being derived from 

 actual analyses rather than from a secondary treatment of them. 

 For these four, in order that only well-known and representative 

 meteorites may be taken, those of Juvinas, Frankfort, Petersburg 

 and Stannern, as given in the writer's list, may be used. The 

 average of these calculated to 100 is shown below and, for com- 

 parison, Washington's average for terrestrial rocks and Merrill's 

 Table V. 



I 



Four 



Meteorites 



Si0 2 49-85 



A1 2 3 11-14 



Fe '°» l 18-87 



MgO . -. 9-S3 



CaO 9-44 



Na„0 0-63 



K 2 0-14 



H 2 



TiO,, 0-03 



P.O. - 0-07 



II 







Ill 



Washington's 







average of 





Merrill's 



terrestrial rocks 





Table V" 



58-24 







45-46 



15-80 







3-21 



7-21 







j -.- 







( 19-29 



3-84 







26-86 



5-22 







2-06 



3-91 







1-11 



3-16 







0-38 



1-79 



MnO 



0-65 



1-04 



Fe, 





+ j-0-98 



•37 







--- 



100-00 100-58 100-00 



That a magma of the composition shown in Table I might 

 differentiate into the present rocks of the earth's crust seems to 

 the writer entirely conceivable. Differentiations much greater in 



* This Journal, (4), xxxv, 324, 1913. 



f Clarke's assumption, Bull. U. S. G. S., 491, p. 22. 



X Publ. Field Museum, Geol. Ser., vol. iii, p. 213, 1911. 



