The composition of this meteorite corresponds very closely with another meteoric-iron from Tucson, discovered by Mr. Bartlett, and described by Prof. J. Lawrence Smith, in the _American Journal of Science_, vol. XIX, page 161. Dr. Smith’s analysis gives Iron 85.54, Nickel 8.55, Cobalt 0.61, Copper 0.03, Phosphorus 0.12, Chromic-oxyd 0.21, Magnesia 2.04, Silica 3.02, Alumina, trace = 100.18. He considers it to correspond to Nickeliferous Iron 93.81, Chrome Iron 0.41, Schreibersite 0.84, Olivine 5.06 = 100.18. By an evident inadvertence Dr. Smith adds the magnesia and silica together, and gives the sum as olivine; these substances are obviously not in the proportions to form the silicate 3 R O, Si O₃, and if we consider the silicate to be olivine, we must reckon the excess of silica as combined with protoxyd of iron. To do this, we must deduct 2.78 from the amount of metallic iron (equal to 2.58 protoxyd of iron), necessary to be combined with the silica and magnesia to give the olivine formula. The amount of olivine contained in the Bartlett meteoric-iron will then be 8.64 per cent. Thus the two masses of iron will be seen to agree very nearly in composition, the only trifling difference being, that Dr. Smith has determined quantitatively the small amount of chromium contained in the Bartlett meteorite, while I have found a little lime and traces of sulphur and chlorine in the specimen you sent to me. The specific gravity I have stated to be 7.39; this was taken on about 12.5 grammes of the iron, and probably is somewhat higher than the portion which I analyzed, as the two surfaces of the larger mass had been rubbed down, and as thus a considerable portion of the exposed silicate would be mechanically removed, it would make the density correspondingly higher. I regret that I had not more of this interesting meteorite at my command, in order to have determined more definitely and satisfactorily the character of the insoluble residue. I shall be glad to make a further investigation of this point if you will supply me with more material. Very respectfully yours, GEO. J. BRUSH. After reading the above letter, Professor Whitney added some remarks on the form and locality of the meteoric iron analyzed by Professor Brush, stating the circumstances under which it came in possession of the city of San Francisco. On the twenty-fourth of November, 1862, the Board of Supervisors of this city received, through Mayor Teschemacher, a letter from General George Wright, commanding the Department of the Pacific, stating that he had received a mass of meteoric iron from General Carleton, commanding the “Column from California,” and which mass he, in accordance with General Carleton’s request, placed at the disposal of the city authorities.