286 MEMOIR ON METEORITES. 



portant point for consideration in regard to the origin of these 

 bodies; as the form alone is strong proof that the individual 

 meteorites have not always been cosmical bodies, for had they 

 been their form must have been spherical or spheroidal. As 

 this is not so, it is reasonable to suppose that at one time or 

 another they must have constituted a part of some larger mass. 

 But as this subject will be taken up again, I pass to another 

 point; namely, the crystalline structure, more especially that 

 of the iron, and the complete separation in nodules, in the 

 interior of the iron, of sulphuret and phosphuret of the metals 

 constituting the mass. When this is properly examined it is 

 seen that these bodies must have been in a plastic state for a 

 great length of time, for nothing else could have determined 

 such crystallization as we see in the iron, and allow such per- 

 fect separation of sulphur and phosphorus from the great bulk 

 of the metal, combining only with a limited portion to form 

 particular minerals; and did we aim to imitate such separation 

 by artificial processes, we could only hope to do it by retaining 

 the iron in a plastic condition for a great length of time. Also, 

 no other agent than fire can be conceived of by which this 

 metal could be kept in the condition requisite for the sepa- 

 ration. 



If these facts with reference to the crystalline structure be 

 admitted, the natural suggestion is that they could only have 

 been thus heated while a part of some large body. 



Another physical fact worthy of being noticed here is the 

 manner in which the metallic iron and stony parts are often 

 interlaced and mixed, as in the Pallas and Atacama irons, 

 where nickeliferous iron and olivine in nearly equal portions 

 (by bulk) are intimately mixed, so that when the olivine is 

 detached the iron resembles a very coarse sponge. This is an 

 additional fact in proof of the great heat to which the meteor- 

 ites must have been submitted, for with our present knowledge 

 of physical laws there is no other way in which we can con- 

 ceive that such a mixture of iron and olivine could have been 

 produced. 



Other physical points might be noticed, but as they are 

 familiar to all, and would add nothing to the theoretical con- 

 siderations, they will be passed over. 



