158 TENTH ANNUAL REPORT OF 



atomic constitution of meteoric anortliite, or of pyroxene, is the same 

 as of tliat which exists in our own rocks. 



An important peculitirity of the stony meteorites is, that their 

 outer surface is covered with a coating strongly resembling pitch ; 

 this is a species of glass formed from the heated condition to which 

 the meteorite arrives in its passage through the air, the heat acquired 

 being sufficient to fuse the outer surface. The black color is due to 

 the protoxide of iron combining with the silica. In most instances 

 the protoxide is formed from the oxydation of the particles of metallic 

 iron in the mass. 



Keei)ing in view then the physical and chemical characters of mete- 

 orites, I propose to offer some theoretical considerations which, to be 

 fully appreciated, must be followed step by step. These views are 

 not offered because they individually possess particular novelty; it is the 

 manner in which they are combined to which especial attention is called. 



The first phjsical characteristic to be noted is their form. No 

 masses of rock^ however rudely detached from a quarry, or blasted 

 from the side of a mountain, or ejected from the mouth of a volcano, 

 would present more diversity of form than meteoric stones ; they are 

 rounded, cubical, oblong, jagged, and flattened. Now, the fact of 

 form I conceive to be a most important point for consideration in re- 

 gard to the origin of these bodies, as this alone is strong proof that 

 the individual meteorites have not always been cosmical bodies ; for 

 had this been the case, their form must have been spherical or sphe- 

 roidal. 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 perfect separation of sulphur and phosphorus from the great bulk 

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

 lar minerals. No other agent than fire can be conceived of by which 

 this metal could be kept in the condition requisite for the separatiori. 

 If these facts be admitted, the natural inference is that they could 

 only have been thus heated while a part of some large body. 



Another physical fact worthy of being noticed liere, is the manner 

 in which the metallic iron and stony parts are often interlaced and 

 mixed, as in the Pallas and Atacama specimens, 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 meteorites must have been submitted ; for, with our 

 present knowledge of physical laws^ there is no other way in which, 

 we can conceive that such a mixture could liave been produced. Other 

 physical points might be noticed ; but as they would add nothing to 

 the theoretical considerations, they will be passed over. 



The mineralogical and chemical points to he noted in meteorites are 



