2341. THE ESTHERVILLE, IOWA, METEORITE— MERRILL. 369 



character of .the latter suggests, however, that it was in a sufficiently 

 liquid form to permeate the siliceous matrix in all directions, and 

 hence the existing cavities may convey little idea of the original 

 amount of shrinkage. However this maybe, the facts given, as a 

 whole, seems to show that the Estherville meteorite is a metamorphic 

 rock.' 



My purpose in giving this detailed description of this more than ordi- 

 narily interesting meteorite is not merely to show the chemical and 

 petrographic nature of the stone as it is to-day. I have felt for some 

 years that in the discussions of the origin of meteorites too little 

 attention has been given to their composition as compared with 

 terrestrial rocks, and to their "life histories," if I may be allowed the 

 expression, as revealed by a detailed study of their primary struc- 

 tural features and those which have been induced by secondary 

 causes.^ 



If it can be shown that certain conditions must have prevailed to 

 produce existing results, while this may not point to a definite 

 source of origin for the body, it will at least narrow the field of specu- 

 lation and can in the future lead to more definite conclusions than 

 have many of the theories and guesses proposed in the past. 



For the privilege of examining and, in some cases, obtaining 

 material for analysis, the author is indebted to Prof. J. E. Wolff, 

 of Harvard University; Prof. Edward Wigglesworth, of the Boston 

 Society of Natural History; Prof. E. S. Dana, of Yale University; 

 Dr. E. O. Hovey, of the American Museum, New York; and Prof. 

 W. H. Emmons, of the University of Minnesota. 



EXPLANATION OF PLATES, 

 Plate 22. 

 estherville, iowa, meteorite. 



Fig. 1. Cleavage fragments of enstatite showing character of material analyzed. 



2. Cleavage fragments of peckhamite showing character of material analyzed. 



3. Section showing angular character of "peckhamite" and illustrating frag- 



mental character of stone. 



4. Section showing angular character of pjToxene. This figure from the same 



. slide as 2. 



5. Section showing angular character and frayed borders of the larger pyroxenes. 



1 It is interesting to compare this view with that expressed by others. Doctor Wadsworth ( I.ithological 

 Studies, pp. 92-101) says: "I can find no evidence in the sections that its materials ever held any other 

 relation than the present one and no sign of a former fragmental state, etc." Mennier (Memoirs, Nat. 

 Acad. Sciences, vol. 13, p. 181), wcoto: "We may suppose that the original mass was in a fragmentary state, 

 partly stony, partly metallic, perhaps accumulated in a crevice, and was there subjected to metalUferous 

 emanations whose product, in the form of a fine network, cemented these independent elements. The 

 remarkable cavities sometimes occurring between the grains of iron and their stony matrices have been 

 artificially reproduced in experiments on the metallic cementation of the powder of peridot by a process 

 previously described." I do not infer from this that Meimier considered the rock clastic in the sense that I 

 am now claiming. 



■i See Merrill, Geo. P. The Composition and Structure of Meteorites Compared with that of Terres- 

 trial Rocks. Smithsonian Report for 1917, pp. 175-188, with 9 plates. 

 1S1404— 21— Proc.N.M.vol.oS 24 



