SORBY'S VIEWS. 107 



give their mutual gravitation a sensible influence, they might grailually collect into 

 masses, and acquire a cohesion more or less compact according to the conditions imposed 

 on such masses during their subsequent history. ... We may, indeed, assert that the 

 meteorites we know have, probably all of them, been originally formed under conditions 

 from which the presence of water, or of free oxygen, to the amount requisite to oxidize 

 entirely the elements present were excluded ; for this is proved by the nature of the 

 miuerals constituting the meteorites, and by the way in which the metallic iron is dis- 

 tributed through them. " * 



In 1864, Mr. 11. C. Sorby announced the presence of gl.ass and gas cav- 

 ities in the olivine of meteorites. He stated that 



" the vitreous substance found in the cavities is also met with outside and amongst the 

 crystals, in such a manner as to sliow tliat it is the nncrystalline residue of the material 

 in which they were formed. ... It is of a claret or Ijrownish color, and possesses the 

 characteristic structure and optical properties of artificial glasses." 



Of the chondritic structure Mr. Sorby says, it appears that 



" after the material of the meteorites was melted, a considerable portion was broken up 

 into small fragments, subsequently collected together, and more or less consolidated by 

 mechanical and chemical actions. . . . Apparently this breaking up occurred in some 

 cases when the melted matter had become crystalline, but in others the forms of the 

 particles lead me to conclude that it was broken up into detached globules whilst still 

 melted." f 



The same year Mr. Sorby remarked that the earliest condition of meteo- 

 rites was that of igneous fusion, but he thought that the Pallas iron afforded 



"physical evidence of having been formed where the force of gravitation was much 

 smaller than on our globe, either near the surface of a very small planetary body, or 

 towards the centre of a larger, which has since been broken into fragments." J 



In 1865, Mr. Sorby developed his views still further, stating : — 



•' The character of the constituent particles of meteorites and their general microscopi- 

 cal structure differ so much from what is seen in terrestrial volcanic rocks, that it 

 appears to me extremely improbable that they were ever portions of the moon, or of a 

 planet, which differed from a large meteorite in having been the seat of a more or less 

 modified volcanic action. A most careful study of their microscopical structure leads me 

 to conclude that their constituents were originally at such a high temperature that they 

 were in a state of vapour, like that in which many now occur in the atmosphere of the 

 sun. ... On cooling, this vapour condensed into a sort of cometary cloud, formed of small 

 crystals and minute drops oi melted stony matter, which afterwards became more or less 

 devitrified and crystallhie. This cloud was in a state of great commotion, and the parti- 

 cles moving with great velocity were often broken by collision. After collecting together 

 to form larger masses, heat, generated liy mutual impact, or that existing in other parts 



* Nature, 1875, xii. 4S5-4S7, 504-507, 520-523. 



t Proo. Roy. Soc, lS63-6i, xiii. 333, 334; Phil. Mag., 1804 (i), xxviii. 157-159; Report Brit. Assoc, 

 1865, XXX7. 139, 1«. 



i Geol. Mag., 1864 (1), i. 240, 241 ; Report Brit. Assoc, 1SG4, xxxiv. (sect.) 70. 



