PROCEEDINGS OP THE GEOLOGICAL SOCIETY. 



7 



The following specimens were exhibited : — 



A specimen of a new Crinoid, exhibited by Mr. Carpenter in 

 illustration of his paper. 



Microscopic sections of Meteorites, exhibited by Dr. Otto Halm, 

 of Keutlingen. 



Tn explanation of the latter the following remarks were addressed 

 on behalf of Dr. Hahn to the President and Fellows present : — 



" Dr. Hahn, in inviting you to examine the microscopical speci- 

 mens of meteorites which he has prepared, and in order to assist 

 you in determining the character of the forms and structures which 

 you will find exhibited in them, desires to present a short summary 

 of the negative considerations which forbid that such structures 

 should be classed among crystalline forms. 



" As is well known, the chondrites, the species of meteorites 

 from which his specimens are prepared, consist, besides the metals 

 which they enclose, of the minerals enstatite and olivine. 



" In his work on the meteorites and their organisms, lately pub- 

 lished, Dr. Hahn has given photographs of 130 different forms and 

 structures. Now if these structures are crystalline, the two 

 minerals in question would present themselves in at least 130 dif- 

 ferent forms and structures, although the absence of all structure is 

 recognized as a fundamental principle of the theory of minerals. 



"Again, the structures exhibited by the chondrites cannot be 

 due to slaty cleavage, since olivine has no slaty cleavage, and that of 

 enstatite and of other minerals does not appear under the micro- 

 scope, or else presents itself there under totally different forms. 



" The greatest importance, however, is to be attached to the total 

 absence of all polarized light exhibited by the two minerals as oc- 

 curring in the meteorites. The contained forms and structures do 

 not polarize the light at all, or only very feebly, although the same 

 minerals, under ordinary circumstances, polarize light very strongly. 

 The absence of all aggregate polarization is especially noticeable, as 

 proving that these objects are not aggregates of crystals. 



" Should we still feel inclined to regard the enclosures as mineral 

 forms, and not as organisms, we must be struck by the utter absence 

 of all crystalline forms, especially in those very minerals which 

 always, and occasionally also in meteorites, appear in a crystallized 

 form. 



" Further, the external forms, and consequently the outlines of the 

 enclosures, harmonize so perfectly with their internal form and 

 structure, that we cannot entertain the idea that these enclosures 

 had been rolled about and ground down before they became finally 

 imbedded in the chondrites. 



" The idea of an aggregate of crystals, if still looked upon with 

 favour, would be contradicted by the fact that the enclosed balls 

 or globes are all constructed excentrically, whereas all terrestrial 

 crystallites are formed concentrically." 



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