234 David Forbes — On Meteorites. 



abruptly terminated, and tliey would fall down with sucli rapidity as 

 to develope by the friction and oxidating effects of the air, intense 

 heat, whereby the external surface would be fused so as to form the 

 vitreous glaze so peculiar to aerolites, whilst at the same time the 

 white hot air would form a luminous envelope around them ; the 

 whole ultimately bursting with one or more explosions, either from 

 the expansion of the gas contained or occluded within the meteorite 

 itself, or, as has been suggested by Haidinger, from the collapse of a 

 sort of vacuum ball formed around them. 



Meunier, who has of late written more copiously than concisely 

 on the subject of meteorites, whilst believing them to be fragments 

 of broken-up planets, regards these bodies as but the last stage in 

 the evolution of planetary bodies, and suggests that the moon is rapidly 

 coming to this stage from the irregularities and incipient fissures 

 visible on its surface, its dissolution not having taken place before, 

 owing to its greater magnitude ; arguing still further, that once broken 

 up into fragments, these would arrange themselves concentrically 

 according to their densities, those which before formed the central 

 part of the planet, which he regards as most heavy and metallic, on 

 the outside, and the others, according to their weight, in the interior. 

 This arrangement he considers accounts for the siderites or meteoric 

 irons having first fallen in the earliest ages of the world, then the 

 siderolites, and afterwards the stone or aerolites proper ; and owing 

 to the meteorites of some recent falls, particularly that of Hessle in 

 Sweden, having contained considerable carbon, he predicts the fall 

 of a totally different class of meteorites in future. These hypotheses 

 seem, however, to be but mere assumptions incapable of proof, for 

 although only some very few instances of siderites having fallen in 

 historic times are recorded, as compared to the much larger number 

 of aerolites, still there is no proof that the proportion was different 

 in prehistoric times, especially as it is well known that the latter 

 would be infinitely more likely to escape observation than the former. 

 Befoi'e concluding, although I fear I have already tried your patience 

 too long, I would still direct your attention to one point more con- 

 nected with the study of meteorites, which is the use of such bodies 

 in the economy of nature ; and unpromising and speculative as such a 

 problem is, I may mention that two attempts, differing widely in 

 their direction, have already been made to solve it. The first of 

 these, made some time back by the German astronomer Mayer, and 

 indorsed by the elaborate calculations of Sir William Thomson 

 (who is understood, however, to have lately changed his opinions), 

 is to the effect that the loss of heat which the sun radiates year by 

 year from its surface, and which is so essential to the well-being of 

 the universe, is restored to it by the continual impact of meteorites 

 falling into its surface; and the other is the still more startling 

 hypothesis of Sir William Thomson himself, which maintains that 

 the origin of life on our globe (and the introduction from time to 

 time of new species) is due to the arrival of aerolites, which, being 

 fragments of other worlds or planets upon which life already 

 existed, had carried with them the germs or seed, or even " living 

 plants or animals," to populate and plant our sphere. 



