6 PEOCEEDINGS OF THE NATIONAL MUSEUM vol.73 



All the evidence at present available, as I interpret it, points to 

 the origin of the metal as introduced at a temperature lower than 

 that of the melting point of the silicates. As above noted, a reduc- 

 tion of a ferriferous silicate either through the aid of carbon or 

 hydrogen is ruled out of consideration by the complete absence of 

 any secondary or residual products. Of all other known meteoric 

 constituents the ferrous chloride, lawrencite, would seem to best 

 meet the apparent necessities of the case. It is found in varying 

 though small proportions an almost universal constituent, and it 

 is permissible to imagine its one-time presence in vastly greater 

 quantities. It is reduced according to Meunier and, as already noted, 

 at a temperature not exceeding 400° C. (750° F.) in an atmosphere 

 of hydrogen. It would seem, then, not too much to assume that this 

 mineral was, as Meunier conceived, the original source, and the frac- 

 tional amount of chlorine found in nearly all meteorites, stony as 

 well as metallic, but an unreduced residue. And further, it is pos- 

 sible to conceive of a hot mass of commingled rock fragments and 

 ferrous chloride, in which the latter is being reduced to the condi- 

 tion of a metallic paste in which the fragments become engulfed as 

 in Figures 3 and 4, Plate 1, or simply cemented as in Figure 1. It 

 must not be forgotten that H. C. Sorby as long ago as 1864 suggested 

 that the metallic constituents of meteorites were introduced into the 

 interstices of the silicates in a state of vapor. 



Such a conception would seem to be particularly applicable to the 

 metal in a stone like that of Estherville, Iowa, in which the iron is 

 in slag or spongelike masses not always closely compacted ,in ail its 

 parts with the silicates.^^ (Fig. 2, lower.) Tschermak's observation 

 on this is of interest. He wrote :^^ 



Das Eisen verhiilt sich oft so, als ob es die letze Bildung ware eine impregna- 

 tion welcbe die zum Thell krystallinisclie, zum Tlieil Tuffartlge masse dur- 

 chdrungen hat. 



Meteorites are unmistakably volcanic products. 



It is fair then to consider the original chloride ,itself a product of 

 volcanic emanations as in terrestrial volcanoes. There would, in 

 result, be this difference, however: The chloride of terrestrial vol- 

 canoes exposed to an oxygen-rich atmosphere manifests itself almost 

 at once as an oxide. In a heated atmosphere of hydrogen or other 

 reduc,ing gases such as it is possible to imagine exists at the fountain 

 source of meteorites a contrary result would be effected and the iron 

 appear in metallic form. 



This source would then be comparable to that of the metal in the 

 basalt of Biihl bei Cassel, Germany, as described by Eitel in his re- 



^^ See Notes on tlie Meteorite of EstlaerTille, etc., Proc. U. S. Nat. Museum, vol. 5S, 1920, 

 pp. 22-24. 



1" Sitz. Kais. Akad. Wien, vol. 88, 1883, p. 253. 



