STRUCTURE OF METEORITES MERRILL. 187 



by Sorby to the effect that " some at least of the constituent particles 

 of meteorites were originally detached glassy globules, like fiery 

 rain." It is possible to conceive that these chondrules, first as blebs 

 of molten matter and then as consolidated particles, may have been 

 triturated in the deep throat of some volcano. The spherical form I 

 can not, however, regard as being wholly due to trituration, a view 

 held by some writers, but rather to their original molten condition. 



The manner in which the metallic portions are wrapped about and 

 even injected into the silicate particles suggests the probable reduc- 

 tion of the iron, not merely since their original crystallization, but 

 even since the reconsolidation of the detritus resulting from their 

 disintegration. 



But one word more. It has long seemed to me that these bodies 

 have not received the attention they merit from the standpoint of 

 world history. 



If we consider, I will not say accept, either the meteoric or plane- 

 tesemal theory of world origin, we are bound, as it seems to me, to 

 regard the meteorites as world matter. 



If so regarded, we are confronted at once with the general basic 

 nature of the original magma from which they were derived. Gen- 

 erously leaving out of consideration the metallic constituents and 

 having regard only for the silicates, it appears that in but a few 

 instances does the silica rise above 50 per cent. Alumina is likewise 

 low, only in the basaltic forms rising even as high as 14 per cent. 

 The percentage of lime is also low, while the alkalies are rarely pres- 

 ent in amounts up to even 1 per cent. Magnesia, on the other hand, 

 is almost invariably abundant, the amount at times rising as high as 

 40 per cent. These facts are well brought out in the accompanying 

 table from a former publication.^ Column I represents an average 

 of 53 analyses with the exceptions noted. Column II shows the 

 average composition of terrestrial igneous rocks, after Clarke, and 

 column III that of the entire lithosphere. 



1 Mem. Nat. Acad, of Sciences, vol. 14, 191G, p. 28. 



