METEOROLOGY. 241 
specific gravity varies from 1.94 to 4.28, being at a mean about 3.5. Some 
masses contain not less than .96 of pure metallic iron, with a little nickel ; 
of this character was the mass weighing 1400 pounds, found in Siberia in 
1749, as also the Mexican specimen found at Zacatecas or Durango, 
weighing from 30,000 to 40,000 pounds, and other masses in all probability 
of meteoric origin. (The largest known aerolites, next to the Mexican just 
mentioned, are, one found in Bahia,.and one near Otumpo in the province 
of Chaco, each from seven to seven and a half feet long, and weighing, the 
former 30,000 pounds, the latter 14,000 pounds.) Other aerolites again 
contain but two per cent. of iron, and some no metallic iron at all. We may 
therefore divide them into two classes: nickeliferous meteoric iron, and 
meteoric stones, properly so called. The metallic iron interspersed in 
almost all gives them a peculiar character; as for the rest, we find in 
meteoric masses the same chemical elements that occur in the earth’s crust, 
namely, eight metals: iron, nickel, cobalt, manganese, chromium, copper, 
arsenic, and tin; five earths: also potash, soda, sulphur, phosphorus, and 
carbon; in all eighteen, or about one third of the known elementary 
bodies. 
With respect to the actual nature and origin of all these phenomena, the 
majority of investigators agree with Chladni that they are of cosmical, not 
atmospherical origin, being in all probability small masses, asteroids, 
moving with planetary velocity, and revolving in space about the sun in 
elliptic or parabolic orbits. Should they come within the sphere of the 
earth’s attraction, they are drawn off their course, becoming luminous on 
entering our atmosphere. The earth’s attraction need not necessarily 
destroy the motion of all these bodies coming within its sphere; the only 
effect may be an alteration in the orbitual motion of the body around the 
sun. We may assume the existence of several meteoric currents, composed 
of innumerable small worlds following each other in a closed ring; the 
different currents probably intersect the orbit of our earth like Biela’s 
comet, and the earth must, among others, pass through two of these 
cuirents in August and November. These asteroids are in all probability 
distributed very unequally in these closed rings, so that there may be only a 
few crowded groups ; such a supposition may explain the rarity of the more 
conspicuous phenomena of this character. It is, to be sure, very enigmatical 
that the meteoric masses commence to shine and to become inflamed at heights 
which are considered as destitute of air. It is also a question, among many 
others which we cannot answer, whether the particles which compose the 
dense mass of a meteoric stone are originally distinct from each other in a 
gaseous condition, and first commence to be drawn together at the time 
they begin to shine ; also, whether from the small shooting stars a compact 
mass may fall, or only a meteoric dust. A hypothesis, broached as early 
as 1660, suggests that meteoric stones may come from the moon, being 
ejected from volcanoes in active operation, a supposition readily refuted by 
the fact, as far as known, of the entire absence of active volcanoes on the 
moon. The older hypotheses of a telluric or atmospheric origin of 
meteoric masses are equally untenable. 
415 
