Page:Popular Science Monthly Volume 58.djvu/438

430 fallen on the earth, also of various kinds of native iron," drew the conclusion that a content of nickel characterized most such bodies. He also found that the meteoric stones were made up chiefly of silica and magnesia and that the iron sulphide of meteorites was distinct from the terrestrial mineral pyrite. He further noted the chondritic structure as characteristic of many of the meteoric stones. The correctness of his observations was soon confirmed by analyses made by Fourcroy, John, Klaproth and others. In 1808 Alois von Widmanstätten, by heating a section of the Agram iron, brought out the figures which have since proved so characteristic of meteoric irons in general and which are now known by his name. Thus the data were early at hand for distinguishing meteorites from terrestrial bodies and it soon became possible to collect the 'sky stones' even when they had not been seen to fall. Systematic efforts for the collection of these bodies were not put forth, however, for many years. Up to 1835 there were only fifty-six different meteorite falls represented in the Vienna collection, and in 1856 only one hundred and thirty-six. Up to 1860 those of the British Museum collection numbered only sixty-eight and those of the Paris collection only sixty-four. The studies of these bodies during the first half of the century were made, therefore, upon a relatively limited number. The earlier investigations were chiefly chemical in character, various elements being discovered in succession. Manganese was discovered in the stone of Siena by Klaproth in 1803, chromium in the stone of Vago by Laugier in 1806, carbon in that of Alais by Thenard in 1808, chlorine in that of Stannern by Scheerer in the same year and cobalt by John in the Pallas iron in 1817. The number of elements discovered since has brought the total up to twenty-nine, none being found, however, which are not already known upon the earth. Many of the chemical compounds of meteorites were early isolated and their identity with terrestrial minerals established. Count Bournon showed in 1802 that the transparent green mineral accompanying the iron of Krasnoyarsk was olivine. The same mineral was found in other meteorites by later observers, and Rose was able in 1825 to make angular measurements of the crystals which showed them to be identical with those of terrestrial olivine. Laugier separated chromite from the stones of Ensisheim and L'Aigle in 1806. Augite was recognized by Mohs in the stone of Stannern in 1824 and by Rose in that of Juvinas in 1825. Haüy recognized a feldspar which he thought to be orthoclase in the stone of Juvinas in 1822, but three years later Rose showed it to be plagioclase; and the existence of orthoclase in meteorites has yet to be proved. Continued investigations of the compounds found in meteorites up to the present time have resulted in the detection of at least twenty-one whose composition is certain, besides several of a somewhat problematic nature. Of these compounds seven have been