METEORITES OF NORTH AMERICA. 413 



Silliman * gave a further account of the meteorite as follows: 



An Eldorado meteoric mass was found by the writer in March, 1872, in the cabinet of Mr. W. H. V. Cronise, of San 

 Francisco, where it was placed by its discoverer, Mr. James H. Grossman who, in 1871, rescued it from the forge of a 

 smith at Shingle Springs, California. It was found in 1869 or 1870 in a field belonging to the same smith about half a 

 mile from the town named. It is said to be the first meteoric mass discovered in California. 



The mass was intact when I first saw it and weighed about 85 pounds avoirdupois. It was flattened upon one side 

 and presented the usual familiar features of iron meteors. It has since been cut in several sections, one of which (which 

 was exhibited with this communication) shows a cross section measuring 12 by 18 cm. The section is approximately a 

 semicircle, having the flattened side for its diameter, with the outline and exterior coating perfectly preserved on all 

 sides. Its weight was over 800 grams. The largest dimensions of the entire mass were about 24 and 29 cm. 



This meteoric mass is remarkably homogeneous in structure and singularly free from the included minerals. Only 

 two very email masses of pyrites, of 3 and 5 mm. diameter, are viable on one side of the slab, and exteriorly I could 

 detect no heterogeneous substance. When the surfaces of the section exhibited were reduced in the planing machine 

 it was observed that the exterior or crust was so much harder than the general surface of the section as to cause the tool 

 to rise a little, thus leaving a distinct margin slightly elevated above the adjacent parts and of a whiter color. This 

 hardened crust had a depth of 4 or 5 mm. 



The density of this iron, determined on a mass of over 750 grams in weight, is 7.875, while the density of the shav- 

 ings cut by the planing tool from the same mass is 8.024, showing a condensation of 0.149 by this mechanical process. 

 This density (of the mass) is above the average specific gravity of meteoric iron, owing probably to its large percentage 

 of nickel, which, as will be observed by reference to the accompanying analysis, is more than twice the average amount 

 of that metal found in other meteoric irons. 



The crystalline structure of this mass is obscure. The Widmannstatten figures are not developed on it by etching, 

 although a confused granular structure was evident after this process. Wishing to test this point thoroughly, I consulted 

 Mr. John E. Gavit of the American Bank Note Company, in New York, who is well known for his microscopic and other 

 scientific tastes. Mr. Gavit very kindly tried all the resources known to the engraver's art with a view to develop, by 

 etching this iron, a surface from which its curious cryptocrystalline structure could be transferred to paper by printing. 

 All of these attempts have proved unsuccessful. The etched surface, however, examined with a lens, shows a reticu- 

 lated structure with numerous brilliant points and V-shaped lines, but so small that when charged with ink the impres- 

 sion upon paper is only a muddy tint. The specimen exhibited shows this peculiar structure developed in four com- 

 partments by different etching agents. Some of the printed impressions taken from this surface were also exhibited. 

 An attempt to develop this cryptocrystalline structure by the aid of a fine "tint" laid on an etching ground by a 

 ruling machine and bitten in, and also by a medallion ruled in orthographic projection, upon which the crystalline 

 lines it was hoped might appear in symmetrical form was not more successful than the other trials. Thus it appears 

 practically hopeless to transfer to paper by printing a structure which may yet be clearly seen by the lens. 



The suggestion, made long since by Berzelius, that the Widmannstatten figures were due to the segregation of the 

 nickel alloy in lines of the octahedron which the etching developed, owing to the inferior solubility of the alloy as com- 

 pared with the pure iron, seems to meet no support from this mass in which the uncommonly high percentage of nickel 

 would naturally lead us to expect a proportionate clear development of the crystalline structure. Is it not rather the 

 probable solution of this structure that it is due to the length of time during which the meteoric mass is kept at a high 

 temperature while slowly cooling? Under such conditions the molecules can rearrange themselves in symmetrical 

 forms and over broad surfaces. In the mass before us it would appear from what has been said of the crust that the 

 heat did not penetrate to a greater depth below the surface than 4 or 5 mm. 



The Cape of Good Hope iron analyzed by Uricochoea resembles this both in the absence of Widmannstatten figures 

 and in its high proportion of nickel, but its cobalt is much larger and there are only five elements found, in place of 

 twelve in the California iron. 



The following analysis was made upon the clean shavings cut from the entire surface of the section by the planing 

 tool, thus securing a perfectly fair average sample. The analysis was made by Mr. F. A. Cairns, assistant in the School 

 of Mines, Columbia College, whose constant devotion to the analysis of iron gives to his work on this metal great trust- 

 worthiness. 



Iron 8L480 



Nickel 17.173 



Cobalt 0.604 



Aluminum 0. 088 



Chromium 0. 020 



Magnesium 0. 010 



Calcium 0.163 



Carbon 0.071 



Silicon 0.032 



Phosphorus 0.308 



Sulphur 0. 012 



Potassium 0.026 



99.987 



