Page:Popular Science Monthly Volume 58.djvu/439

Rh found to differ in composition from any known terrestrial substances. The character of these indicates the complete absence of water and of oxygen in any large amount from that portion of nature's laboratory where meteorites are formed. Important investigations as to the gases occluded by meteorites were begun by Boussingault in 1861 and have been continued by Wright, Ansdell, Dewar and others. It has been proved that large quantities of hydrogen, as well as carbonic acid gas, are contained in these bodies, under pressure greater than that of the earth's atmosphere. These investigations led further to the spectroscopic study of meteorites by Vogel, Wright and Lockyer. The spectra thus obtained when compared with those exhibited by comets showed striking resemblances, which have led to a growing belief among scientific men in the identity of origin of comets and meteorites. Lockyer has indeed pushed this conclusion to the point of believing that "all self-luminous bodies in the celestial spaces are composed either of swarms of meteorites or of masses of meteoritic vapor produced by heat," and he draws from this many important deductions relating to the origin of the stars, comets and nebula?, and the physical conditions prevailing in them. It will remain for the twentieth century to test the correctness of such conclusions, but the facts already brought out have considerably shaken the confidence hitherto placed in the nebular hypothesis. Another interesting result of the century has been the establishment of a general similarity between shooting stars and meteorites. This idea was first suggested by Chladni in 1798, but it has remained for Newton, Adams and Schiaparelli to give it shape and proof. The general verdict of science is now in accord with the belief of Newton, "that from the faintest shooting star to the largest stone meteor we pass by such small gradations that no clear dividing lines can separate them into classes." Moreover, the longexisting belief in le vide planétaire, space filled only with a mysterious fluid called ether, has been shown to be untenable. Careful records and estimates have shown that 20,000,000 cosmic bodies large enough to produce the phenomena of shooting stars are encountered by the earth daily. The number of these bodies existing in space must be, therefore, beyond all calculation, and their existence implies that of smaller particles in sufficient number to form a widely pervasive cosmic dust. Many remarkable meteorite falls have occurred during the century. Beginning with the stone shower of L'Aigle in 1803, when 2,000 to 3,000 stones fell, no less than eleven such showers have been recorded. In the shower of Pultusk, Poland, which occurred in 1868, 100,000 stones are estimated to have fallen, their total weight reaching over 400 pounds. In the shower at Mocs, Germany, in 1882, more than 3,000 stones fell. In our own country about 750 pounds of meteoric matter fell at Estherville, Iowa, in 1879, and several thousand stones fell over an area nine miles in