THE ORIGIN AND STRUCTURE OF METEORITES. 385 



oxygen of the air which burns, not only the charcoal, but also the silicon 

 in the pig and a part of the iron. The black scoria which is formed in 

 the process often contains a peridote with a base of iron, having the 

 same chemical constitution and crystalline form as the magnesian peri- 

 dote of the eruptive rocks of the earth and of the meteorites. 



The simple oxidation of silicon develops an enormous quantity of 

 heat, very much more than the combustion of carbon ; a heat which 

 is sufficient to refine the metal in the retorts of iron and steel works 

 without the addition of carbon. Silicon, which in nature has passed 

 wholly into the state of silicic acid, or been burned, must, at the mo- 

 ment of its combination with oxygen, have been the cause of an intense 

 heating both in our own globe and in the other stars, which are also 

 composed of silicates. But in the last, of which meteorites are the 

 fragments, the temperature was not probably so high as in the metal- 

 lurgical furnaces and the experiments we have cited. It is, in fact, 

 very remarkable that, notwithstanding their tendency to a distinct 

 crystallization, the silicate compounds of which the meteorites are con- 

 stituted are only in the condition of very small and quite confused 

 crystals, as if they had not passed through fusion. We might say 

 that, rather than the long needles of ice which liquid water forms in 

 freezing, their fine-grained texture resembles that of frost and snow, 

 which is known to be due to the immediate passage of atmospheric 

 aqueous vapor to the solid state. 



In brief, the extreme tendency of the oxidation of silicon to pro- 

 duce the formation of peridote, daily proved in our laboratories and 

 shops, is no less evidently manifested in the deeper rocks of our globe, 

 on the one side, and in the distant stars from which the meteorites 

 come, on the other side. Everywhere are observed the effects of an 

 ancient and vast oxidation. In this we have a simple and experi- 

 mental explanation of the ubiquity of peridote. It is the universal 

 scoria. 



As a forest shows at a glance the plant-life of all ages, the universe 

 presents us stars in all the phases of their existence, from that of incan- 

 descent heat to obscurity, and an advanced cooling. We have also 

 just seen that some of them are in demolition, and that their frag- 

 ments fall upon others, to which they remain attached. The numer- 

 ous falls of meteorites on our globe teach us that this fact, instead of 

 being an exception, answers to an habitual regime. And the constitu- 

 tion of the meteoric masses teaches us with certainty that the celestial 

 bodies whence they emanate have a chemical history quite similar to 

 that of the interior regions of our planet. 



So, while the exploration of the sky reveals to us millions of worlds 

 beyond our solar system, our planet, small as it is, offers us an example 

 of the changes which the stars have undergone, and an episode in the 

 general history of the universe. The meteorites form a kind of line 

 of union between the succession of the epochs of the earth, the object 

 vol. xxix. 25 



