162 



TEE GEOLOGiyX. 



It is a curious but well-known fact that substances which do not 

 possess a crystalline structure may be made to take it under the 

 influence of mechanical forces ; thus, iron becomes crystalline by 

 repeated percussion, and above we have an example of a crystalline 

 structure being given by pressure. The foregoing facts will also tend 

 to explain why coal sometimes takes the form of hexagonal prisms in 

 contact with trap-rock. The rhombohedron and the hexagonal prisms 

 are certainly the crystalline forms of carbon in the state of coal and 

 graphite ; whilst the diamond, as is well known, crystallizes in forms 

 derived from the cube or the regular octahedron ; whence carbon is 

 dimorjyJioiis. 



M. Wohler, Professor of Chemistry in the University of Gottingen, 

 has sent to the Academy of Sciences at Paris the following description 

 of the composition of a meteoric stone : — 



I have just made the analysis of a meteoric stone which fell at 

 Kuba in Hungary on the 15th of April, 1857. The aerolite in 

 question is black, and its colour is owing to amorphous coal. It also 

 contains — besides those elements generally found' in meteorites — a 

 certain quantity of organic matter, that is to sa,y, a carburet of hy- 

 drogen similar to parafiine, to cozokerite, or to scheererite. The quan- 

 tity of this bituminous matter is certainly very small but I have 

 assured myself of its presence by the most incontestable proofs. This 

 organic matter is soluble in alcohol, and becomes carbonized by calci- 

 nation. I have since found the same organic matter in the meteoric 

 stone which fell in 1838 at the Cape of Good Hope. This stone is 

 also of a black colour, and contains 1*5 per cent, of carbon. It is 

 probable that this bituminous matter is a product of organic nature, 

 and that the presence of coal in these meteoric stones is to be attri- 

 buted to the action of heat upon the bituminous matter whilst the 

 meteorite was in an incandescent state, i. e. during its passage through 

 the terrestrial atmosphere." 



This remarkable discovery, which we have given in the author's 

 own words, would appear to be favourable to those philosophers who 

 still look upon meteoric stones as products of our earth. We should 

 not, however, without reluctance abandon another opinion : — When 

 the periodicity of remarkable falls of aerolites became tolerably cer- 

 tain, Arago, in 1839, wrote : "We thus become more and more con- 

 firmed in the belief that there exists a zone composed of millions of 

 small bodies, the orbits of which cut the plane of the ecliptic at about 

 the point which our earth annually occupies between the 11th and 

 13th of November; it is a new planetary world beginning to be 

 revealed to us.'' {Anauaire, 1839.) 



It is now almost doubtless that there are other periods besides the 

 November one. 



Sir Isaac Newton once said tliat he took all the planets to be com- 

 posed of the same matter as the eiu'th, namely, earth, water, and 

 stone, but variously concocted. " Recalling to mind the remarkable 

 interview between Newton and Conduit at Kensington," says. Alex. 



