METEORITES OF NORTH AMERICA. 13 



terrestrial factors: (1) density of population, (2) character of population, (3) climate, and 

 (4) character of soil. Density of population will increase the number of meteorites known from 

 a region, because the greater the population the greater the number of observers and the more 

 numerous the chances both that the meteorite will be observed when it falls and that it will be 

 found after it has fallen. As regards character of population, a high order of intelligence is 

 favorable not only to the observation but to the preservation of meteorites. The writer has 

 elsewhere called attention * to the fact that the distribution of meteorites on a map of the 

 world is almost exactly that of the Caucasian race. This seems to prove quite conclusively that 

 the distribution of meteorites is largely dependent on the degree of civilization attained in a 

 region. That this factor is more important than density of population is shown by the fact that 

 no meteorites are known from China in spite of its immense numbers of people. In the province 

 of North America it is hardly likely that the different degrees of intelligence existing in different 

 regions would exert any discernible influence on the number of meteorites known. As regard 

 climate, aridity may be doubtless considered favorable and humidity unfavorable to the preser- 

 vation of meteorites. In a humid climate the iron meteorites disintegrate much more rapidly 

 than in an arid climate, and to a certain extent the same is true of stone meteorites. 



As regards character of soil, it is obvious that soils free of rocks would be most favorable 

 to the finding of meteorites. The existence of such soils in Kansas and Texas has led to the 

 discovery in those regions of meteorites that would probably have been overlooked in stony 

 localities. An iron meteorite is, of course, more likely to attract attention in any soil than a 

 stony meteorite, but the latter is quite likely to be overlooked in stony soils. From the above 

 it appears that the most favorable terrestrial conditions for the finding of meteorites are those 

 of a dense, intelligent population living in an arid climate and upon a pebbleless soil. Such 

 conditions are not likely to exist together, but now one and now another will predominate in 

 any given region. To a certain degree the absence of one is likely to offset the presence of another, 

 but where several of these conditions are lacking and a preponderance of meteorites occurs 

 other reasons must be sought. The eastern States of the United States as compared with the 

 western States possess a relatively dense population, but a moist climate and rocky soil. Canada 

 has a scanty population, a moist climate, and rocky soil. Mexico has the advantage of an arid 

 climate but the disadvantage of a scanty and an illiterate population, and a more or less rocky 

 soil. 



No evidence has been obtained in the preparation of the catalogue which proves to the 

 writer that the individual meteorites of a single shower may be scattered over wide areas. No 

 observed shower has ever been known to distribute individuals over an 'area greater than 16 

 miles in length. Only complete similarity between more widely separated meteorites should 

 warrant belief in more extended showers, and such similarity has never been established. A 

 considerable likeness exists, it is true, among the medium octahedrites of the southern Appa- 

 lachians, but a careful study of the history and structure of each discloses differences too great 

 to warrant their being classed together. Another group of North American meteorites showing 

 strong similarity is that of Coahuila. These are hexahedrites and are reported from localities 

 the most extreme of which are nearly 300 miles apart. As hexahedrites are relatively rare 

 among meteorites, it hardly seems probable that several would fall within a hundred miles of 

 each other, although this is by no means impossible. It is of course true that there may have 

 been artificial distribution, but of this there seems to be no positive evidence. A considerable 

 uncertainty, however, attaches to the statements of the localities where the specimens were 

 found, and until the localities can be more definitely established, either by new finds or by 

 reliable evidence regarding the old finds, the question as to whether they represent parts of a 

 widely distributed shower must remain an open one. 



Important meteorite collections are possessed, at the present time, by seven institutions in 

 North America: The American Museum of Natural History, Amherst College, Field Museum of 

 Natural History, Harvard University, Mexican National Museum, United States National 

 Museum, and Yale University. Of these, the Yale University collection is probably the oldest. 



i Pop. Sd. Hon., 1904, p. 352. 



