554 



Mr. G. Ansdell and Prof. J. Dewar. [June 10, 



The actual amount of water given off after this exposure to a moist 

 atmosphere was considerably less than what was obtained in the 

 original heating of the meteorite, and from this we infer that the 

 water is chemically combined in the stone. It would be difficult to 

 explain, otherwise than by chemical combination, the power by which 

 the water is retained by these meteorites, as it is not given off until a 

 very high temperature is reached. In any case it is clear that the 

 hydrogen must come from the action of water on the iron nickel 

 alloy, or finely disseminated carbon. Greville Williams has pointed 

 out that the large amount of hydrogen obtained from heating finely 

 divided zinc-dust is not due to free hydrogen, but to the action of the 

 zinc on the hydrated oxide of zinc. 



We now pass on to the consideration of the vaTious graphites 

 examined. The celestial graphite was a perfect oblong nodule weighing 

 30 grams, which had been taken from the interior of a mass of the 

 Toluca meteoric iron. It had a uniform dull- black colour, except at 

 one end where there was a slight incrustation of sulphide of iron. Its 

 fracture showed a uniform dull black, compact mass ; it was easily 

 pounded up in a porcelain mortar, and formed a fine granular powder 

 without any lustre. 



On extracting the gases from this specimen a considerable quantity 

 of marsh-gas was obtained, so that it appeared to us most important 

 to compare it with some samples of terrestrial graphites, more espe- 

 cially as the occluded gases had, to our knowledge, never before been 

 determined in these bodies. 



For this purpose four samples of native graphites were obtained. 

 The Cumberland graphite was a magnificent specimen of the original 

 Borrodale, and had been in a private cabinet for over fifteen years. It 

 had the characteristic dense homogeneous structure, and brilliant 

 external lustre of the graphites coming from this district. The 

 Siberian example was from the Alexandref Mine ; its structure was 

 columnar and striated, with little external lustre ; it was rather more 

 easily broken up than the Borrodale, but formed the same dull black 

 powder. The specimen from Ceylon was of the type usual to that 

 island ; highly . lustrous and flaky, breaking up very easily, and 

 forming small shining plates when ground up. The last sample, 

 which was from the same cabinet as the others, but whose origin 

 was unfortunately unknown, had a dull external surface, was exceed- 

 ingly porous, and much, more brittle than any of the previous ones, 

 grinding up very easily into a dull black powder. It had more the 

 appearance of the celestial graphites, which was heightened by having 

 slight incrustations of sulphide of iron in its surface. Its low specific 

 gravity also shows it to be some exceptional variety. 



It seemed to us most important in connexion with this subject to 

 examine some matrix with which the graphites are usually found 



