Page:Popular Science Monthly Volume 29.djvu/396

382 from their original bed. Like the lavas, they are composed chiefly of silicates.

We observe, in the first place, that most of the eruptive rocks differ considerably from meteorites. The most important point of contrast is that the latter contain nothing resembling the arenaceous or fossiliferous matters of which the stratified beds are constituted—that is, nothing suggesting the action and movement of an ocean or the presence of life. A great difference also appears in comparison with the masses on which the sedimentary beds immediately rest. Thus, we never find granite, or any of the minerals associated in it, in meteorites. The analogies of meteorites must be sought in the silicate rocks, which originate in deep regions, below the granite.

A striking example of this similitude is afforded by the recent lavas, which are formed from the association of two silicates, pyroxene and anorthite feldspar, and which correspond exactly with the meteorite picked up at Jonzac (Charente-Inférieure) on the 15th of June, 1819, and with that one which fell at Juvinas, in the department of Ardèche, on the 13th of June, 1821. Peridote, which is remarkably constant in meteorites, also occurs in the eruptive masses, often abundantly.

An equally remarkable fact is the absence from meteorites of the whole series of rocks which form an important part of the crust of the globe. It may be explained by supposing that the meteoric stones that reach us come exclusively from the internal parts of planetary bodies constituted as our globe is, or that those bodies are destitute of quartziferous silicates, like granite, as well as of the stratified beds. In the latter case, those stars have suffered less complete revolutions than our planet, and exhibit no traces of the co-operation of an ocean by which most of the crust of the earth above the internal masses has received its shaping.

A recent unexpected discovery, made by M. Nordenskiöld in Greenland, has shown the resemblances we have just described to be closer and more complete. It is worthy of remark that, notwithstanding the abundance with which iron is diffused in all parts of the crust of the earth, that metal has never been found in the native state. However pure and rich may be the mineral, some kind of a process is necessary to extract the metal contained in it. This peculiarity is due to the sensitiveness of iron in the presence of chemical agents, particularly of oxygen. Sir John Ross brought back from his arctic voyage, in 1818, some knives with blades formed of pieces of iron which the Esquimaux said came from scattered blocks not far from Cape York. The analysis of this iron showing the presence of nickel, a meteoric origin was attributed to it. Other samples of iron, offering similar characteristics, were brought down from the North by other explorers. M. Nordenskiöld's attention was attracted to some of these specimens, which had been deposited in the museum at CopenhaganCopenhagen [sic], and prompted