Page:Popular Science Monthly Volume 58.djvu/440

432 length and one mile wide near Forest City. Iowa, in 1890. Many oi these falls have been marked by extraordinary phenomena of light and sound, making them events never to be forgotten by those who witnessed them and worthy to be reckoned among the most remarkable natural occurrences of the century. About two hundred and eighty-five actually observed meteoric falls is the total recorded during the century. It is a remarkable fact regarding the nature of the material fallen that only five of these have been of meteoric irons. One of these irons fell at Mazapil, Mexico, during the star shower of November, 1885, at the time when the return of Biela's comet was looked for, and was thus considered an occurrence corroborative of the already suspected relationship among comets, shooting stars and meteorites.

The indifference to the collecting of meteorites which characterized the early part of the century has given place in its latter days to an extraordinary diligence in the search for these bodies. One meteorite has of late acquired a value equal to four times its weight in gold and several can be sold for two and three times their weight by the gold standard. The meteorite collection of the Natural History Museum in Vienna has for many years been the leading one. What it has cost to build it up may be known from the fact that it is considered the most valuable of any single collection in that great treasure house. Representatives of over five hundred meteoric falls are exhibited in this collection, and the meteoric matter has a total weight of seven tons. The collection of the British Museum of Natural History is nearly as large, while at Paris, Berlin, St. Petersburg and Calcutta, together with Washington, Chicago, Cambridge and New Haven, in our own country, are gathered extensive and important collections. The establishment of such large collections has for the first time put the study of meteorites on a satisfactory basis and given lively hope that important truths will be discovered by researches thus made possible. The general similarity of the stony meteorites to the basic volcanic rocks of the earth has been established, and similarity of many physical structures such as brecciation, slicken-sided surfaces and veins has been proved. The chondritic structure and the crystalline structure represented by the Widmanstätten figures are, however, so far as is yet known, peculiar to meteorites, and it will remain for the twentieth century to discover what these structures mean. Classifications of meteorites based on their mineralogical and structural characters have been established, and important differences among meteorites shown, in spite of their family resemblances. It would be idle perhaps to recount, as might be done, many theories regarding the nature and origin of meteorites which have been found untenable as a result of the century's study. The theory of the lunar origin of meteorites had at times such able supporters as Laplace and J. Lawrence Smith. Other able observers have believed