402 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XIII. 



gratelike forms are met with in which the crossbars are curved, and sometimes extend entirely across the face of the 

 chondrus, or again show short and interrupted forma. The olivines of the groundmass are always fragmental. 



The enstatite, like the olivine, occurs both in the form of chondri and as scattered fragments in the groundmass. 

 It is distinguishable from the olivine by its gray color, less transparency, well-developed cleavages parallel to the 

 vertical axis, and by its insolubility in acids. The position of the plane of the optic axes could not be made out with 

 certainty with the instrument at command, but as the mineral is biaxial, nonpleochroic, and extinguishes always 

 parallel with the vertical axis, there is apparently no doubt as to its true nature. The chondri are sometimes composed 

 wholly of enstatites, with small quantities of interstitial amorphous base, of olivine and enstatite together. The dis- 

 tinction between the two minerals is, owing to their small size and imperfect development, often impossible by the 

 microscope alone. A more common form of the enstatite is that of irregular fragments with a radiating or fan-shaped 

 structure. Other quite perfectly spherical, very minute forms occur, consisting of an almost wholly amorphous mater- 

 ial or with only faint beginnings of crystallizations shown by rays of light radiating across the surface aa the stage is 

 revolved. The exact mineralogical nature of these can not be determined. 



The metallic iron occurs in lumps and in very irregular areas, or as injected drops in the interior of the chondri. 

 It is of a silvery-white color by reflected light, and readily distinguished from the pyrrhotite with which it is nearly 

 always associated, and which shows a bronze-yellow luster. In a few instances grains or chondri of olivine or ensta- 

 tite are entirely surrounded by a dark border of iron and pyrrhotite, as Tschermak has figured from sections of the 

 Cabarras meteorite. In such cases the iron often penetrates slightly into the mass of the mineral, having evidently 

 exercised a corrosive action. 



The structural features of the groundmass are, as already observed, very obscure. It consists of minute angular 

 particles of olivine and enstatite embedded in a matrix so fine and so badly stained by iron oxide's that its true nature 

 can not be satisfactorily ascertained. From the fact that this coloring matter has become so thoroughly disseminated 

 throughout the whole mass, I am inclined to regard it as tuffaceous. A wholly granular, glassy, or partially devitri- 

 fied base would seemingly have proven less pervious and shown the ferruginous staining only along lines of fracture and 

 cleavage. 



The chemical investigation of the stone was rendered somewhat unsatisfactory owing to the badly oxidized con- 

 dition of the metallic portions. For the results given below I am indebted to Mr. J. E. Whitfield, of the U. S. Geolog- 

 ical Survey. The complete analysis gave: Metallic portion, 6.21 per cent; soluble in hydrochloric acid, 52.19 per 

 cent; insoluble in hydrochloric acid, 41.60 per cent. Specific gravity, 3.57. The metallic portion yielded: 



Fe Ni Co 



88.25 11.27 0.48 =100.00 



The soluble portion is presumably all olivine, together with pyrrhotite and secondary iron oxides. An analysis 

 of this portion -was rendered of no value from the fact that the first attempt at a complete separation of the two silicate 

 minerals by digestion in dilute hydrochloric acid was a failure, and the badly weathered condition of the stone rendered 

 a second attempt scarcely worth the while. The insoluble portion was separated by prolonged digestion in dilute 

 hydrochloric acid, followed by boiling sodic carbonate. The remaining powder showed under the microscope very 

 pure enstatite fragments, together with rarely a minute grayish particle that acted but faintly on polarized light and 

 the exact mineralogical nature of which could not be ascertained. Mr. Whitfield's results on this powder were aa 

 follows: 



. SiO 2 54. 42 0. 91 



FeO 14.03 0.19] 



CaO ' 2.46 0.041 0.95 



MgO 29.11 0.72J 



100.02 



This, it will be observed, is a highly ferriferous enstatite (bronzite) with perhaps a small admixture of a lime-bearing 

 pyroxenic mineral as indicated by the microscope. The relative proportions of the various constituents as they existed 

 in the fresh rock, can not be estimated with any degree of certainty from the figures as above given for the reasons 

 already stated. * * * 



Meunier 2 remarked concerning the meteorite as follows : 



This is a very exceptional stone at first sight and one upon which we possess only a brief note by Merrill. 



The stone is granular, of a reddish-brown color and only shows its metallic elements upon the polished surface. 

 In thin sections under the microscope its meteoric nature becomes apparent ; chondrules of enstatite of more than 1 mm. 

 in diameter detach themselves in the midst of limpid crystals of which the most abundant are peridotic, and opaque 

 grains where can be readily seen nickel iron and pyrrhotine or magnetic sulphide of iron. 



Specific gravity at 11, 3.59. The magnet extracts from it 7.02 per cent of the magnetic substance. The residue, 

 92.98 per cent, separates under the action of the acid into 52.13 per cent of attackable minerals and 40.75 per cent of 

 pyroxenic compounds. These figures differ but little from those of Whitfield. 



On comparing the meteorite of San Emigdio with the rare masses preserved in the museum it appears that the 

 cosmic rock called belajite most nearly approaches it. It is a very interesting type and one which demands fresh study. 



