Page:Popular Science Monthly Volume 29.djvu/765

Rh are many facts about these stones which imply that violent forces have in some way acted during the meteorite's history. The brecciated appearance of many specimens; the fact that the fragments in a breccia are themselves a finer breccia; the fractures, infiltrations, and apparent faultings seen in microscopic sections, and by the naked eye—these all imply the action of force. M. Daubrée supposes that the union of oxygen and silicon furnishes sufficient heat for making these materials. If this is possible, those transformations may have taken place in their first home. Dr. Reusch argues that the repeated heating and cooling of the comet as it comes down to the sun and goes back again into the cold, is enough to account for all the peculiarities of structure of the meteorites. These two modes of action do not, however, exclude each other.

Suppose, then, a mass containing silicon, magnesium, iron, nickel, a limited supply of oxygen, and small quantities of other elements, all in their primordial or nebulous state (whatever that may be), segregated somewhere in the cold of space. As the materials consolidate or crystallize, the oxygen is appropriated by the silicon and magnesium, and the iron and nickel are deposited in metallic form. Possibly the heat developed may, before it is radiated into space, modify and transform the substance. The final result is a rocky mass (or possibly several adjacent masses) which, sooner or later, is no doubt cooled down throughout to the temperature of space. This mass in its travels comes near to the sun; powerful action is there exerted upon it. It is heated. How intense is that heat upon a cold rock unprotected apparently by its thin atmosphere it is not possible to say. We know that the sun's action is strong enough to develop and drive off into space that immense train, the comet's tail, that sometimes spans our heavens. It is broken in pieces. We have seen the portions go away from the sun, to come back probably as separate comets. Solid fragments are scattered from it, to travel in their own independent orbits.

What is the condition of the burned and crackled surface of a cometic mass or fragment as it goes out from the sun again into the cold? What changes and recrystallizations may not that surface undergo before it comes back again to pass anew through the fiery ordeal? We have here forces that we know are acting. They are intense, and act under varied conditions. The stones subject to those forces can have a history full of all the scenes and actions required for growth of such strange bodies as these that come down to us. Some of our meteors, those of the star-showers, certainly had that history. What good reason is there for saying that all of them may not have had the like birthplace and life?

Before I close, let me add one lesson that has been taught us by recent star-showers. The pieces which come into our air in any recurring star-shower belong to a group whose shape is only partly known. It is thin, for we traverse it in a short time. It is not a uniform ring,