466 MEMOIRS NATIONAL ACADEMY OF SCIENCES, VOL. XIII. 



Finally, as the composition of the isolated olivine: 



Si0 2 45. 82 44. 91 



FeO (by difference) 1. 75 2. 08 



CaO 3. 30 1. 33 



MgO 49. 13 51. 44 



100. 00 99. 76 

 Specific gravity, 3.24 to 3.27 (by methyl iodide). 



SiO 2 : MgO+CaO+FeO 1 : 1.719 1: 1.791 



As the olivine, according to the result of the microscopical examination and according to the proportion of 

 KO : Si0 2 in the case of the isolation with HC1, was not altogether unchanged, a further portion of the Carleton iron 

 was treated with copper ammonium chloride, which, in accordance with previous experiments did not noticeably 

 affect the olivine, although a small portion was dissolved. The isolated grains appeared under the microscope color- 

 less, transparent, and entirely unaltered. They gave the following composition: 



Si0 2 43. 29 



FeO 52 



CaO 1. 13 



MgO 54. 92 



99.86 

 Specific gravity, 3.199. 



SiO : FeO+CaO+MgO 1 : 1.95 



It is thus certain that we have here a forsterite with a small mixture of monticellite. The small amount of iron 

 would not change this conclusion even if it could not, as is possible, be referred mainly or entirely to inclusions. The 

 alkalies could not, for lack of material, be determined; but since plagioclase was observed only very sparingly in the 

 thin sections, it can not compose more than a fraction of 1 per cent of the silicate at most. The entire or almost entire 

 absence of iron oxide in the olivine, although iron was present in so considerable quantity, is explained by the fact 

 that the oxygen present only sufficed to oxidize the magnesia and silica, which have a greater affinity for oxygen than 

 iron, nickel, and cobalt. 



The composition of the nickel iron is in both masses so near alike that the percentage of nickel and cobalt does 

 not differ materially (10.59 per cent and 10.52 per cent); the proportion of the two elements is, however, very different 

 (Co 1.41 and 0.98 per cent), and the difference is so great that it can not be ascribed to a mistake in the analysis. 



The great excess of silica in both total analyses is inexplicable. It is also found in the analyses by Smith, Brush, 

 and Genth and was the occasion of Fletcher's reckoning from the latter an olivine with about 24 per cent iron oxide 

 In this direction a still further investigation is desirable. 



If this excess of silica be disregarded and the small amount of iron in the olivine which is apparently due to inclu- 

 sions of nickel iron be overlooked, the following composition may be given for Carleton. For Ainsa, were the necessary 

 data at hand, almost the same figures would suffice. 



Nickel 

 iron 



Fe 84.02 84.63 89.32 



Ni 8.63 8.89 9.18 



Co 1.33 1.37 1.41 



Cu 03 .03 .03 



Cr 02 .02 .02 



C... .04 .04 .04 



94.07 Nickel iron... 



100.00 



2. 10 43. 58 

 . 06 1. 14 



2. 66 55. 28 



100.00 100.00 100.00 100.00 



The specific gravity was determined by Leick (at 19.8 C.) as 7.2248; disregarding the accessory material, that for 

 the nickel iron was as 7.7357. Carleton takes on a strong permanent magnetism and has a quite strong coercion force. 



As already stated, the ring-shaped (Ainsa) mass is in the United States National Museum ; 

 the kidney-shaped (Carleton) mass in the California State Mining Bureau, San Francisco. 

 Small sections are to be found in several collections. 



