Page:The Solar System - Six Lectures - Lowell.djvu/28



. If the mass be large, time does not suffice to fuse more than its exterior, and the interior retains the cold of interplanetary space. As Young tells us, one of the fragments of the Dhurmsala meteorite in India was found in moist earth, half an hour or so after its fall, coated with ice!

But their speed is the real tell-tale upon their past. An ingenious investigation by the late Professor Newton, whose specialty was these very things, proved that ninety per cent., and probably all of the meteorites for which we have sufficient data, were traveling, before their encounter with the earth, in orbits not parabolic, but elliptic, like those of the short-period comets, and were moving direct. They come to us, therefore, not from the stars, but from the Sun's own domain. They, too, then are members of the system.

Most interesting is their constitution in its bearing upon their origin. Some are stone, some iron—meteoric iron joined with nickel. Now the iron meteorites are saturated with occluded gases, which can be extracted from them by suitable processes, and which cannot have been occluded originally except in the molten interior of a sun, intense heat and excessive pressure being necessary; and as they are now ungathered in remnants of our own once nebulous mass, they must betray