HANDBOOK OF THE METEORITE COLLECTIOISTS. 9 



was early noted, but it was not until 1855 that J. Lawrence Smith 

 found the material in the condition of a soft solid of a green-brown 

 color in the meteoric iron of Tazewell County, Tenn.^ In 1877 ^ he 

 also noted the occurrence of the substance in the iron of Eoclringham 

 County, N. C. In this same year Daubree noted its occurrence in the 

 terrestrial iron of Ovifak, Greenland,^ and proposed for it the name 

 lawrencite in honor of its first discoverer. The material liquefies on 

 exposure to the atmosphere, the iron passing over quickly to the con- 

 dition of sesquioxide. It is this feature that brings about the rapid 

 disintegration of so many irons and causes the stone meteorites to 

 become rust-brown or freckled with rust-colored spots. 



Metallic constituents; nickel-iron alloys. — These are essentially the 

 same in all meteorites. They occur in varying proportions from a 

 fraction of 1 per cent, as in the Bishopville stone, to upward of 90 per 

 cent, as in the so-called iron varieties. In the stones the form is that 

 of disconnected drops or stringers; in the pallasites that of a more or 

 less disconnected mesh or sponge enfolding silicate minerals; and in 

 the metallic forms constituting nearly the entire mass. Etching by 

 means of a weak acid, the polished surface of a meteoric iron will in 

 the majority of cases give rise to an interesting series of marldngs 

 known under the name of Widmanstiitten figures, after a German 

 chemist who first brought them to public notice. They are due to the 

 unequal solubility of the three alloys of iron and nickel which make 

 up the mass of the material. Two of these alloys occur in the form 

 of thin plates and are known by the terms 'kamacite and taenite. A 

 third alloy, known as plessite, fills the space formed by the intersec- 

 tion of these plates (see etched slices of the Casas Grandes and Toluca 

 irons, pis. 16 and 35). The composition of these alloys has not been 

 absolutely determined, owing to the difficulty of separating them one 

 from another, and it is considered probable that the so-called plessite 

 is but a mixture or intergrowth of the other two. Davison gives the 

 composition of the two first named as determined on separations 

 made from the Welland, Canada, iron, as follows: 



»Amer. Journ. Sci., vol. 19, 1855, p. 154. 

 8 Idem, vol. 13, 1877, p. 214. 

 •Compt. Rend., vol. 84, 1877, p. 66. 



