62 Farrington — Nature of the Metallic Veins, etc. 



of many of the siderolites is that of a metallic network enclos- 

 ing grains of the silicates, while on the other hand the tend- 

 ency of the metallic grains of many aerolites to a continuous 

 arrangement has been noted by Eeichenbach* and Newton. f 



Between meteorites of the siderolite structure and those in 

 which the metallic constituents occur only as isolated grains 

 there are all gradations. Hence sheets or filaments of a con- 

 tinuous network might remain in some portion of a meteorite, 

 while in the remainder the metallic constituents would be 

 present only as isolated grains. Favorable cross sections of a 

 continuous network would appear as veins. Metallic filaments 

 which are undoubtedly of this character are to be seen in sections 

 of the Crab Orchard (E-ockwood) and Bluff meteorites now in 

 the Field Museum collection. The nickel-iron appears in general 

 in the sections in the form of isolated grains, but over a por- 

 tion it appears as continuous filaments. These are the only sec- 

 tions in the collection which show such filaments but there is 

 every reason to believe that the filaments could be found on 

 sections of other meteorites if looked for. If the writer's 

 view be correct, therefore, the term filament would describe 

 these structures better than the term veins, since the latter 

 term implies fissures filled subsequent to their origin. 



*Pogg. Annalen, vol. cviii, pp. 291-311. 

 f This Journal, III, xlv, p. 152. 



Field Columbian Museum, 

 Sept. 1, 1900. 



