384 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XIII. 



The stony material, when treated with chlorhydric acid over a water bath, aSords soluble part 47.80 per cent, 



insoluble 52.20 per cent, and is constituted as follows: 



Soluble part. Insoluble part. 



Silica 34.55 57.81 



Iron protoxide 27.75 11.04 



Alumina trace 0. 23 



Lime trace 5.31 



Magnesia 36.38 24.97 



Chromium oxide 0. 10 



Soda. . 0. 46 0. 84 



99. 14 100. 30 



I separated some of the globules perfectly free from the intervening matrix, which is easily done by rubbing a 

 piece of the stone between the fingers. Very minute specks of iron could be distinguished upon them, and when 

 pulverized and treated with hydrochloric acid they give about the same result as the matrix, viz, soluble 46.80 per 

 cent, insoluble 53.20 per cent, and the magnesia in the soluble part was 34.48 per cent, showing clearly that they were 

 merely concretions of the matrix of the stone. 



The nickeliferous iron, which was separated mechanically, is composed of 



Iron 94. 49 



Nickel 4 12 



Cobalt.. .51 



99.12 



The quantity of iron was too small for an examination of the other constituents, as phosphorus and copper, but 

 they were no doubt both present. 



Mineral constituents of the stone. -Careful examination under the microscope of the broken surface, as well as of 

 a section rubbed down very thin, shows the stone to be composed of the unisilicates and bisilicates usually found in 

 these bodies, mixed with nickeliferous iron and troilite; nothing like anorthine is distinguishable. The first two 

 minerals constitute the bulk of the stone, and there is possibly more than one variety of each of these minerals present. 

 The nickeliferous iron is quite abundant, though Professor Shepard states that from a casual observation he estimates 

 it at 1 per cent. By the careful method adopted for separating it, I find in two average specimens over 10 per cent. 

 The particles of iron are very bright and lustrous, looking as if they were covered with plumbago, although there is 

 no evidence of the presence of the latter mineral. The troilite is not detected so readily by the eye as it is by chlor- 

 hydric acid. One of the spherules was rubbed down to a thin section and examined by polarized light, and in this 

 way it was found to contain both classes of silicates referred to, a fact, as already stated, sustained by chemical exam- 

 ination. I consider the mineral constituents of the Rochester stone to be about as follows: 



Bronzite and pyroxene minerals 46. 00 



Olivine minerals 41. 00 



Nickeliferous iron 10. 00 



Troilite 3. 00 



Chrome iron 15 



Meunier 6 classes the meteorite as Montrejite, and Brezina 7 as spherical chondrite. 

 The meteorite is distributed, Harvard possessing the largest quantity, 75 grams. 



BIBLIOGRAPHY. 



1. 1877: NEWTON. Meteor of December 21, 1876. Amer. Journ. Sci., 3d ser., vol. 13, pp. 166-107. 



2. 1877: SHEPARD. On the meteoric stone of Rochester, Fulton County, Indiana. Idem, pp. 207-211. 



3. 1877: SMITH. Note of the recent fall of three meteoric stones in Indiana, Missouri, and Kentucky. Idem, p. 243. 



4. 1877: KIRKWOOD. The meteor of December 21, 1876. Amer. Philos. Soc., vol. 4, pp. 592-595. 



5. 1877: SMITH. A description of the Rochester, Warrenton, and Cynthiana meteoric stones, which fell respectively 



December 21, 1876, January 3, 1877, and January 23, 1877, with some remarks on the previous falls of meteorites 

 in the same regions. 1. Rochester (Indiana) meteorite. Amer. Journ. Sci., 3d ser., vol. 14, pp. 219-222. 



6. 1884: MEUNIER. M6teorites, pp. 231, 237-238, and 494-495. 



7. 1885: BREZINA. Wiener Sammlung, pp. 185 and 233. 



Rockingham County. See Smith's Mountain. 

 Rockwood. See Crab Orchard. 



