^HT. 2. THE SHAEPS, VIRGIjSTIA, METEORITE WATSON. 3 



The ratio of phenocrysts to glass base in the glass porphyritic 

 t3^pe of chondriile is subject to some variation, but the phenocrysts 

 are always in excess (pi. 2, fig. 2) . Except for a rare euhedral olivine 

 phenocryst both the olivine and the enstatite of the chondrules are 

 fragmental in appearance and are of angular or subangular outline. 

 In origin Doctor Merrill regards these as " rock fragments reduced 

 to their present form through mechanical attrition." ^ He says : 

 ■" In brief, their present structural peculiarities, both external and 

 internal, are entirely inconsistent with any conceivable theory of 

 •origin but that of detrital particles from solidified magmas." 



The fragmental nature of the stone is strikingly shown in the 

 angular fragments of both olivine and enstatite set in the dark brown 

 ground. Some of these approach in size the larger chondrules, with 

 smaller broken, angular ones of the same composition and form, 

 ■so distributed about the larger ones as to afford unmistakable evi- 

 dence of mechanical derivation. 



A large number of measurements made on thin sections of the 

 •stone showed the chondrules and silicate fragments to range in size 

 from a maximum of 0.63 mm. by 0.56 mm., and a minimum of 0.008 

 mm. by 0.008 mm. Of the total number of measurements, 37 per cent 

 were equidimensional bodies, 52 per cent were of bodies whose 

 diameters were in the ratio of 1.2 to 1.8, and 11 per cent exceeded the 

 ratio of 2 to 1. 



The following analysis of the Sharps stone I am permitted to 

 use through the courtesy of Dr. George P. Merrill, of the United 

 States National Museum, for whom it was made by Dr. J. E. Whit- 

 field under a grant from the National Academy. 



Per cent. 



Metallic portions 9.69 



Rock material 87. 89 



Troilite 2. 42 



100.00 

 The metallic portion has the following composition: 



Per cent. 



Iron 8S. 54 



Nickel 9.91 



Cobalt 1. 39 



Phospliorus trace 



Sulphur 0. 15 



99. 99 



The silicate portion freed from metal and troilite has the compo- 

 sition given in column 1 below, and recalculated with the propor- 

 tionate amounts of metal and troilite as already given, in column 2. 



' Merrill, G. P. : On Chondrules and Chondritic Structure in Meteorites. Proc. Natl. 

 Acad. Sci., vol. 6, p. 449, 1920. 



