THE S TR UC TURE OF ME TE ORI TES 6 1 



of parallel bands and partly also by the above described Neu- 

 mann lines. Sheen, Neumann lines, and parallel banded struc- 

 ture of the cubic meteorites will be found on close examination 

 to characterize the kamacite of many octahedral irons {schraffir- 

 ten kamazit of Reichenbach), while the kamacite of other octa- 

 hedral irons is wholly granular {fleckig kamazit of Brezina) . 



Regarding the part played by the different alloys in the 

 process of crystallization, opinions differ, though the general 

 opinion is that the kamacite crystallized first and the other 

 substances arranged themselves accordingly. Sorby likened 

 the process to the forming of needles of ice on the surface 

 of water, leaving angular spaces which were filled later. J. 

 Lawrence Smith on the other hand, thought that the foreign 

 minerals, such as schreibersite, separated and crystallized first 

 and the purer alloys followed. Huntington is of a similar opin- 

 ion and draws attention to the close resemblance in appearance 

 between Widmanstatten figures and the arrangement of inclu- 

 sions of magnetite in mica in support of the view. 



Most authorities agree that the crystalline structure exhibited 

 indicates that the masses must have remained for a long time in 

 a fused or viscous state from which they cooled but slowly. 

 The conclusion of Tschermak was that "the greater number 

 of meteoric irons exhibit a structure which indicates that each 

 formed a part of a large mass possessing similar crystalline char- 

 acters and the formation of such large masses presupposes long 

 intervals of time for tranquil crystallization at a uniform temper- 

 ature." Sorby reached a similar conclusion and regards the 

 Widmanstatten figures "as the result of such a complete separa- 

 tion of the constituents and perfect crystallization as can occur 

 only when the process takes place slowly and gradually. They 

 appear to me to show that the mass was kept for a long time at 

 a heat just below the point of fusion." 



2. Iron-stone meteorites. — The metallic portions of most mete- 

 orites of this class show Widmanstatten figures on etching. The 

 mineral silicates entering into the composition of the mass also 

 often exhibit well-defined crystal forms, the perfection of which is 



