TABLE XIII. (R+Cu.) Internal resistance, 150 centimeters of copper wire included. (b) 150 *7492 150 2 4 150 6 150 16 8.53 9.74 11-11 13:07 14:41 144 16:32 14-02 *2606 3:57 496 21:15 22-98 0 100 " 11:15 130 14-79 16:35 17-89 18:36 19:37 19:45 20:16 20:39 20-28 21:57 22 83 TABLE XIV. (R+Cu.) Internal resistance, 200 centimeters of copper wire included. 550; wire. 8888888887 Rheochord. •1282 5-69 •1149 •1016 200 200 200 *3099 4.17 4.65 200 •2868 4.35 4.84 200 2681 4.52 5.03 9-75 10-85 12-68 13-97 14:43 15-29 15:52 14:29 200 2358 4.72 5-26 9-98 11-12 12-97 14:21 14.69 15:49 15-74 15:20 16:30 200 •2262 ⚫0828 4-92 5-48 10:40 11.70 13-71 15-17 15.91 17:06 17-86 18:39 21-30 29.12 •1806 5:34 5-94 11-28 12-76 14-79 16:21 16-97 17-95 18-61 19-02 20-22 21:26 19-6 0901 Mean values for 50, 60 and 70, 12:45 14-09 161 17:43 18-17 19-0 19-54 19-89 20-62 21-14 20:43 20-95 19-81 "80, 90 & 100, 12-94 1454 16:58 17 86 18:57 19:34 19-99 20-15 20-77 21-20 20-68 21.14 30-80 50 to 100, 12-69 14:31 16:34 17-64 18-37 19-17 19-76 20-02 20-69 21:17 20:56 21-04 20:30 except the last one, 23-44. (0) Tangent. Resistance per wire. True, inter. resistance. AM. JOUR. SCI.-SECOND SERIES, VOL. XLIII, No. 127.-JAN., 1867. ART. VIII.-On Colorado Meteorites-Russel Gulch Meteoric Iron, and Bear Creek Meteoric Iron; by Prof. J. LAWRENCE SMITH, Louisville, Ky. THE first of these irons I described in the September number of this Journal, calling it the "Colorado meteorite." Owing to the discovery of another in the same territory (specimens of which have been in my possession for some little time), it will be proper to designate the first mass as the "Russel Gulch" iron and the other as the "Bear Creek" iron. Of this last there are two short notices in the November number of this Journal, pages 260 and 286, the specimen of it in my possession has enabled me to make a thorough examination of the constituents. The piece I have has a portion of the exterior attached. As has already been stated by Prof. Shepard, it is coarsely crystalline, and laminated from the effects of decomposition between the crystals; the surface contains considerable pyrites, although Prof. Shepard did not discover any in his specimen. I was enabled to separate and analyze magnetic pyrites, schreibersite and nickeliferous iron. Of the magnetic pyrites sufficient was separated to make a quantitative determination which was as follows: The schreibersite was not obtained in sufficient quantity for a complete analysis; about 50 milligrams of the pure mineral gave all the constituents usually found in this interesting mineral. The nickeliferous iron, constituting of course the great bulk of of the mass, was composed as follows: The lamina of iron are often very brilliant, having the luster of silver and caused me to suspect more nickel than was found. It was supposed that in the decomposition of the crystals the iron would disappear more rapidly than the nickel, and that by a process of cementation, the nickel would accumulate in the laminæ; but from careful examination of the process of decomposition, there is no doubt that the interior of the mass will not differ materially in its composition from the analysis already. given of the nickeliferous iron. Besides the minerals already mentioned, and which properly belong to the original mass, there is much oxyd of iron, containing some nickel arising from the decomposition of the surface. ART. IX.—On a new locality of Tetrahedrite, Tennantile, and Nacrite, with some account of the Kellogg Mines of Arkansas; by Prof. J. LAWRENCE SMITH. A SHORT time since Prof. E. T. Cox of Indiana sent to me an antimonial copper ore containing silver, one fragment being the termination of a crystal having a number of small but beautiful faces, another was a minute crystal of a different form; in the hands of Prof. Cox a blowpipe analysis had given about five per cent of silver in some of the mineral. The crystalline fragments were first examined and they enabled me clearly to trace out tetrahedrite in one and tennantite in the other. The faces on the tetrahedrite were small but beautiful and very numerous; from the number on the fragment examined there would not have been less than from 60 to 70 had the crystal been perfect: it corresponds very nearly to the cyrstal figured in Dufrenoy's Mineralogy, plate 124, fig. 441, which he speaks of as coming from Moschellandsberg, a locality that I am not able to discover. Good measurements were made on a few of the faces. P on P 70°; P on b3 159° 30′; P on a2 144° 30' Specific gravity of different specimens varied from 4-78 to 5-08; the latter was the sp. grav. of the above crystal. The analysis of two specimens, No. 2 being a part of the crystal, The quantity of No. 2 analyzed did not exceed 300 milli grams. There are two minerals consisting of minute micaceous scales on the quartz containing this gray copper. One of them I could not obtain in sufficient quantity for examination; from an imperfect examination I conclude that it is muscovite; the other mineral, a soft unctuous talc-like mineral, is nacrite, composed as follows; These minerals came from an exceedingly interesting mine in Arkansas that is as yet almost unexplored; I have obtained a full description of it from Prof. Cox and I think it would be well to give it here, for besides being likely to prove of considerable commercial value when properly explored, there will doubtless be found many interesting mineral species there. The Kellogg mines are situated 10 miles north of the city of Little Rock in Pulaski Co., Ark. The country in the vicinity is rolling, the highest hills are about 270 feet above the water level of the neighboring streams. The surface rocks are thick and thin beds of sandstone alternating with shales occupying the base of the coal measures. The rocks are but little disturbed and are for the most part horizontal. There are no metamorphic rocks showing themselves at the surface nearer than Little Rock on the south side of the Arkansas river. Innumerable veins of milky quartz are seen traversing the sandstones and shales. About seventeen years ago lead ore was discovered at these mines by Mr. Kellogg, companies were organized and mining operations carried on extensively for about one year, when the flattering accounts of the gold discoveries in California caused the miners to leave, and the work which had been badly conducted was abandoned. Many tons of the ore which is an argentiferous galena (containing 60 to 200 ounces of silver to the ton) were extracted from the mine and finally the greater part was shipped to England and sold at a good price. A smelting furnace has been erected on the grounds, but for lack of skill, the proprietor never succeeded in working the ore profitably, consequently the impression was produced that the ore could not be smelted, but there is no good reason for such an opinion. Since the mines have been abandoned, the old shafts, ranging in depth from fifteen to seventy feet, are all filled in, and the country has become covered with a dense undergrowth of brush |