﻿302 Huntington — Crystalline Structure of Iron Meteorites. 



alloys of zinc and antimony have been described by Professor 

 Cooke,* and in the alloys of copper and zinc by Prof. F. H. 

 Storer.f They correspond to that pasty condition so well 

 known to plumbers and workers in alloys. We here refer 

 only to the conditions of the plessite ; but at times we also 

 find the whole meteoric mass divided up by small cracks, and 

 thus rendered so friable that it can readily be broken into 

 coarse polygonal grains with a hammer. Such a disintegration 

 must have been a mechanical one, affecting the whole mass sub- 

 sequent to its solidification. It is similar to the well-known 

 effects produced on iron by long-continued jarring, and may 

 have been the result of the violent concussions which are 

 kpown to be caused by the passage of the meteorite through 

 the air. We have recently had the opportunity of examining 

 a specimen of aluminium bronze sent to the Laboratory of 

 Harvard College by Professor C. F. Mabery of Cleveland, Ohio, 

 which most strikingly illustrates the effect here described. The 

 bronze, consisting of 90 per cent copper and 10 per cent 

 aluminium, had been cast into a bar and reheated for forging. 

 When the heated bar was laid on an anvil and struck with a 

 hammer, it broke up into small polygonal grains, just like 

 those of the Cosbj^'s Creek and Seelasgen meteorites. 



Such products as have been described all point to a very 

 slow cooling of the molten metal out of which the crystals 

 came, and this is the opinion held by the best observers in re- 

 gard to this process. Thus Mr. Sorby writes: "These facts 

 clearly indicate that the Widmanstatt's figuring is the result of 

 such a complete separation 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 mete- 

 oric iron was kept for a long time at a heat just below the 

 point of fusion, and that we should be by no means justified in 

 concluding that it was not previously melted. Similar princi- 

 ples are applicable in the case of the iron masses found in 

 Disco ; and it by no means follows that they are meteoric, be . 

 cause they show the Widmanstatt's figuring. Difference in the 

 rate of cooling would serve very well to explain the difference 

 in the structure of some meteoric irons, which do not differ in 

 chemical composition ; but as far as the general structure is 

 concerned, I think that we are quite at liberty to conclude that 

 all may have been melted, if this will better explain other 

 phenomena.":): ■ Similar opinions have been expressed by 

 Tschermak and Haidinger. 



We have tried in this paper to establish the following 

 points : — 



* Memoirs of the American Academy, New Series, vol. v, pp. 336-371. 

 f Ibid., vol. viii, pp. 27-56. % Nature, 1877, vol. xv, p. 498. 



