COMPOSITION AND STRUCTURE OF METEORITES 41 



redness, it gradually assumes the granular structure shown in Figure 2. 

 If the heat be continued for a sufficient period, the octahedral structure 

 will entirely disappear and the iron show only the granular structure. 

 This feature has has been noted and described by Berwerth *^ of the 

 Vienna Museum, who applied to it the name metabolism, and to 

 irons in which the change had taken place that of metabolites.^^ 

 Some irons, Hke that of Roeburne, Australia, which, so far as known, 

 have not been heated since reaching the earth, show a combination 

 of the two structures, and others are wholly granular. Are these 

 octahedral irons which, in their wanderings have become highly heated, 

 perhaps by too close proximity to the sun, and become thus meta- 

 morphosed? Who shall say? It is at least something worth thinking 

 about. 



The ultimate source of the metal has likewise been a matter of 

 speculation. By Daubree and some others it has been thought to 

 have been derived, by a process of reduction, from some iron-rich 

 silicate such as olivine. This is, however, extremely improbable since 

 nowhere are there evident signs of the process in its incomplete stage. 

 Moreover, the olivine fragments in such iron-rich forms as that of 

 Admire, Kans., are all perfectly fresh and sharp as so many frag- 

 ments of broken glass. That the iron was never in a molten condition 

 is shown not only by the uncorroded condition of the silicates, but 

 by the physical condition of the metal itself, which is not that of a 

 metal cooling from fusion, like ordinary "cast iron," but is rather 

 that of the soft, malleable material commonly known as "wrought 

 iron" which may be smelted from its ores at a comparatively low 

 temperature. It seems, therefore, altogether probable that the metal 

 results from reduction from the chloride form and that the small 

 amount of this material now found as lawrencite is but a residue, 

 as was suggested by Meunier several years ago.^^ 



That it plainly was not a portion of the molten magma from which 

 the other constituents crystallized out is shown further by the position 

 it often occupies relative to the silicate constituents as shown in 

 Plates 20 and 21, where it is found as a mere film enwrapping chon- 

 drules and crystal fragments indicating an extreme degree of fluidity. 

 It is possible to conceive of this having been brought about through 

 the percolation into the interstices of the porous tuft' of a gaseous or 

 liquid chloride, afterwards to be reduced.^^ Such a reduction, as 



89 Sitz. der Kais. Akad. der Wiss., vol. 114, May 1908. 



'd That the granular structure might be secondary was first suggested by Sorby in 1887. He did not prove 

 definitely that it might be produced artificially by heating. 



" See Concerning the Origin of the Metal in Meteorites, by George P. Merrill, Proc. U. S. Nat. Mus., 

 vol. 73, Art. 21, pp. 1-7, pis. 1-3, 1928. 



" The Estherville meteorite oflers a strong argument in favor of the origin of the metal through chloride 

 reduction. This meteorite is a metamorphosed conglomerate, quite slaglike in portions, and the metal 

 often occurs only partially filling the cavities as would naturally be the case did not the supply of material 

 continue throughout the reducing process, the chloride consisting of but 44.1 per cent of iron and 55.9 per 

 cent chlorine. 



