ZOOLOaY AND BOTANY, MICK08C0PY, ETC. 723 



able by the naked eye. " These celestial fossils* tell us of a planet on 

 which aquatic life was sufficiently developed to produce them and to 

 preserve them after death by a process of infiltration with siliceous 

 material, which dissolved the lime of which their structure must have 

 consisted as far as their inorganic constituents are concerned, and 

 supijlanted it by the various kinds of siliceous materials, filling up 

 also the interstices and openings which had formerly contained organic 

 substance. This planet, therefore, must have had a comj)aratively long 

 period of existence ; it must have had an atmosphere, and its surface 

 must in whole or in part have been covered by water. . . . Since 

 bacteria are known to I'C able to withstand a temperature of — 100^ C. 

 without losing vitality, the Thomson-Richter hypothesis of the 

 propagation of life through the universe becomes almost a tangible 

 reality." 



Dr. Hahn recently sent microscopical sections to the Geological 

 Society, and on his behalf the negative considerations were pointed 

 out,t which forbid that such structures should be classed among 

 crystalline forms : — 



" The chondrites, the species of meteorites from which the 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, 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 different forms and structures, 

 although the absence of all structure is recognized as a fundamental 

 principle of the theory of minerals. Again, the structures exhi- 

 bited 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 Microscope, 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 occurring 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 inclosures 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 

 inclosures, harmonize so perfectly with their internal form and 

 structure, that we cannot entertain the idea that these inclosures have 

 been rolled about and ground do^m before they became finally 

 imbedded in the chondrites. 



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



* See article by G. W. Rachel. 'Science,' ii. (1881) pp. 275-7. 

 t Quart. Journ. Geol. Soc, xxxvii. (1881) Proc. p. 7. 



