232 David Forbes — On Meteorites. 



been used foi' macadamizing roads, and which, after having been 

 taken up by a whirlwind, had descended subsequently by their own 

 weight. Another suggestion was, that they originated from the 

 condensation of vapours arising from the earth, an idea which 

 appears to have been entertained by Kepler, and which in various 

 modified forms has reappeared from time to time. Thus, Fusinieri 

 imagined meteorites to be derived from gases, holding metallic 

 matters in solution, present in the upper strata of our atmosphere, 

 which suddenly coalesced and condensed themselves into such solids. 

 It is hardly necessary to state that the chemical composition of the 

 atmosphere proves it not to contain the elements of meteorites, and 

 physically it is almost beyond conception to imagine the vast quantity 

 of the enormously attenuated atmosphere requisite to form by its con- 

 densation a solid like the masses of meteoric iron previously referred 

 to. Something like this idea was also brought forward much more 

 recently in France ; the supposition being that our atmosphere was 

 charged with what was termed meteoric dust, which contained iron, 

 nickel, and the other elements of meteorites, and from which they 

 were formed by a similar process of condensation. It was even 

 asserted that such dust could be collected on the summits of our 

 higher mountains, but neither facts nor theory corroborate this 

 hypothesis any more than the former. That they came from the 

 sun is an opinion alluded to by Diogenes Laertius, and also by 

 Anaxagoras, who was persecuted by the theologians of his day be- 

 cause he maintained that the sun must be a molten fiery mass. 

 Pliny ridiculed this idea, but some forty years ago the late Mr. 

 Brayley advanced the suggestion that meteorites were formed by the 

 condensation of the gaseous emanations from the sun, and considered 

 this view borne out by Sorby's discovery that some parts of 

 meteorites had a structure probably due to sublimation and segrega- 

 tion. Still more recently, in 1870, Mr. Williams, in his work on 

 the fuel of the sun, considers them to be solar projectiles which had 

 passed the boundaries of the zodiacal light, and brings to his aid 

 the recent spectroscopic discoveries of the preponderance of hydrogen 

 in the sun's atmosphere, in connexion with the fact of that gas being 

 found occluded in meteoric iron. 



It would also appear that the ancients held the idea that the 

 aerolites fell from the moon, for Pliny and other writers mention 

 their watching for falls of stones from the sky during the eclipses of 

 the moon ; an occurrence which the Syrians still believe takes place 

 on clear moonlight nights. When in later times the moon's surface 

 was shown to be eminently volcanic, the conjecture that meteorites 

 might be bodies projected from volcanoes in the moon became 

 generally entertained, and was investigated by Laplace, Olbers, and 

 others ; Laplace's calculations militating against this hypothesis by 

 showing that even if thrown out of a volcano of the moon with an initial 

 speed of 7771 feet per second, they would require two days and a half 

 to reach the earth, which would be a speed far less than the number 

 of miles per second we know them actually to travel at. The same 

 argument also refutes the idea that they might have been bodies 



