Fiision-Struclurcs in Meteorites. BOO 



Secondly, it has been determined that similar strnctures occur 

 in terrestrial igneous formations, different in kind and coming 

 from different localities, yet each bearing this same mark. 



The chemical compoisition of certain eruptive rocks, is often 

 very similar to that of meteorites ; in fact, so closely do the 

 figures of analysis of certain lavas agree with those of some me- 

 teorites, that this analogy of composition has been regarded as 

 one of the mainstays of tlie neveriheless untenable theory, that 

 would assign to meteorites a terrestrial volcanic source. 



The origin and method of formation of igneous rocks have 

 been thoroughly investigated and studied ; it is well known that 

 these rocks have once ail been in the state of fusion, and that 

 then, cooling, slo\vly or rapidly, according to existing conditions, 

 they finally attained the solid state. 



1 have not been able to give more than a cursory glance at 

 Vogelsang and Zirkel's valuable work, " Die Krystalliten," yet 

 1 believe myself to be only bearing out the observations there 

 noted, in stating, that on the cooling of mineral masses from a 

 state of fusion, frequently there separate — or perhaps segregate — 

 from the main mass, minute granules, globular in form, wliich 

 granules will be found scattered through the mass. 



I am not aware whether any explanation of this phenomenon 

 has been offered and accej)ted ; but to me it seems most likely, 

 that as the mass is not homogenous in composition, certain 

 parts of it, yielding up their heat more readily than the sur- 

 rounding portions, would naturally contract slightly, and thus 

 form minute particles or globules by themselves in the mass. 

 In support of this suggestion, I may sate tluit, in nearly all, if 

 not in all_, cases which I studied, the miteri.d forming the 

 structure appeared to be of a different nature from the matter 

 immediately surrounding it. 



If a section be taken through a spheroidal body, the resulting 

 cut will be either a circle or of a shape more or less elliptical, 

 according to how the section was made. 



The sti'uctures encountered, as has been shown, all present 

 rounded or curved outlines ; in some cases even approaching 

 very closely to a circle. 



Resting, then, on all these facts revealed by observation, I 

 feel justiticd in declaring, that tlieife structures represent sec- 



