476 SMITHSONIAN MISCELIvANEOUS COLLECTIONS VOL. 52 



Wahl's klino-enstatite.^ Other monoclinic forms show the polysyn- 

 thetic twinning so characteristic of the Renazzo stone. In addition 

 to the above-named siHcates are numerous small and irregular inter- 

 stitial areas of a completely colorless, transparent, isotropic, or 

 sometimes weakly doubly refracting mineral without cleavage lines 

 or twin striae, which would ordinarily pass for a glass. These, as in 

 previous cases,® I have considered, for lack of evidence to the con- 

 trary, to be maskelynite, basing my determination on Tschermak's 

 figures and descriptions in plates i6 and 17 of his Die Mikroskopische 

 Beschaffenheit der Aleteoriten. 



The stone will be known, in accordance with the usual custom of 

 naming, as the Thomson meteorite. 



EXPLANATION OF PLATES 



The Thomson, Georgia, Meteorite 



Pl. LVn, Figs, i and 2. Two views. Natural size. Fig. 2 shows a polished 

 surface, on which, at the right and near the end, is a broad, illy defined 

 black vein. A small threadlike vein evidently starting from the same 

 source extends upward and to the left, with frequent branching, to the 

 highest point on the polished surface. In photographing this view the 

 specimen was tilted a trifle more than in Fig. i in order that the light 

 might so fall as to bring out the fractured surface on the lower margin. 



The Thomson, Georgia, Meteorite 



Pl. LVIII, showing microstructure. The black areas are of metallic iron and 

 iron sulphide ; the small, white interstitial areas the supposed maskelynite. 

 The large chondrule at the middle of the left margin is enstatite. Else- 

 where in the plate the silicates are not well differentiated. 



'Die Enstatitaugite, etc., Helsingfors, 1906. 



• vSee description of Stony Meteorite from Coon Butte, Ariz., Am. Jour. Sci., 

 May, 1906, p. 351, and On the Meteorite of Rich Mountain. N. C, Proc. U. S. 

 N. M., vol. 32, 1907, p 243. 



