(25.) 1868, January 30.—It is obviously a matter of much importance that the composition and general characteristics of aerolites, together with the phenomena attending their fall, should be carefully noted; as such facts have a direct bearing on the theory of their origin. In this regard the memoirs of Professors J. G. Galle, of Breslau, and G. vom Rath, of Bonn, on a meteoric fall which occurred at Pultusk, Poland, on the 30th of January, 1868, have more than ordinary interest. These memoirs establish the fact that the aerolites of the Pultusk shower entered our atmosphere as a swarm or cluster of distinct meteoric masses. It is shown, moreover, by Dr. Galle that this meteor-group had a proper motion when it entered the solar system of at least from 4½ to 7 miles per second.
The foregoing list contains but a small proportion of the meteoric stones whose fall has been actually observed. But, besides these, other masses have been found so closely similar in structure to aerolites whose descent has been witnessed, as to leave no doubt in regard to their origin. One of these is a mass of iron and nickel, weighing 1680 pounds, found by the traveler Pallas, in 1749, at Abakansk, in Siberia. This immense aerolite may be seen in the Imperial Museum at St. Petersburg. On the plain of Otumpa, in Buenos Ayres, is a meteoric mass 7½ feet in length, partly buried in the ground. Its estimated weight is about 16 tons. A specimen of this stone, weighing 1400 pounds, has been removed and deposited in one of the rooms of the British Museum. A similar block, of meteoric origin, weighing more than six tons, was discovered some years since in the province of Bahia, in Brazil.
General Remarks.
1. A Committee on Luminous Meteors was appointed several years since by the British Association for the Advancement of Science. This committee, consisting at present of James Glaisher, F.R.S., Robert P. Greg, F.R.S., Alexander S. Herschel, F.R.A.S., and Charles Brooke, F.R.S., report from year to year not only their own observations on aerolites, fire-balls, and falling stars, but also such facts bearing upon the subject as can be derived from other sources. An analysis of these reports justifies the conclusion that meteoric stone-falls, like star-showers, occur with greater frequency than usual on or about particular days. These epochs, established with more or less certainty, are the following:
| (a.) | January | 4th. |
| (b.) | " | 16th. |
| (c.) | " | 29th. |
| (d.) | February | 10th. |
| (e.) | " | 15th—18th. |
| (f.) | March | 6th. |
| (g.) | " | 12th. |
| (h.) | April | 1st. |
| (i.) | " | 10th—14th. |
| (j.) | May | 8th—9th. |
| (k.) | " | 13th—14th. |
| (l.) | " | 17th—19th. |
| (m.) | June | 3d. |
| (n.) | " | 9th. |
| (o.) | " | 12th. |
| (p.) | " | 16th. |
| (q.) | July | 3d—4th. |
| (r.) | " | 14th—17th. |
| (s.) | August | 5th—7th. |
| (t.) | " | 11th. |
| (u.) | September | 4th—10th. |
| (v.) | October | 13th. |
| (w.) | November | 5th. |
| (x.) | " | 12th—13th. |
| (y.) | " | 27th—30th. |
| (z.) | December | 5th. |
| (z´.) | " | 8th—14th. |
| (z´´.) | " | 27th. |
2. It is worthy of remark that no new elements have been found in meteoric stones. Humboldt, in his "Cosmos," called attention to this interesting fact. "I would ask," he remarks, "why the elementary substances that compose one group of cosmical bodies, or one planetary system, may not in a great measure be identical? Why should we not adopt this view, since we may conjecture that those planetary bodies, like all the larger or smaller agglomerated masses revolving round the sun, have been thrown off from the once far more expanded solar atmosphere, and have been formed from vaporous rings describing their orbits round the central body?"
3. But while aerolites contain no elements but such as are found in the earth's crust, the manner in which these elements are combined and arranged is so peculiar that a skillful mineralogist will readily distinguish them from terrestrial substances.
4. Of the eighteen or nineteen elements hitherto observed in meteoric stones, iron is found in the greatest abundance. The specific gravities vary from 1.94 to 7.901: the former being that of the stone of Alais; the latter that of the meteorite of Wayne county, Ohio, described by Professor J. L. Smith in Silliman's Journal for November, 1864, p. 385.
5. The average number of aerolitic falls in a year was estimated by Schreibers at 700. Baron Reichenbach, however, after a discussion of the data at hand, makes the number much larger. He regards the probable annual average for the entire surface of the earth as not less than 4500. This would give twelve daily falls. They are of every variety as to magnitude, from a weight of less than a single ounce to over fifteen tons. The baron even suspects the meteoric origin of large masses of dolerite which all former geologists had considered native to our planet.
6. An analysis of any extensive table of meteorites and fire-balls proves that a greater number of aerolitic falls have been observed during the months of June and July, when the earth is near its aphelion, than in December and January, when near its perihelion. It is found, however, that the reverse is true in regard to bolides, or fire-balls. These facts are susceptible of an obvious explanation. The fall of meteoric stones would be more likely to escape observation by night than by day, on account of the relatively small number of observers. But the days are shortest when the earth is in perihelion, and longest when in aphelion; the ratio of their lengths being nearly equal to that of the corresponding numbers of aerolitic falls. On the other hand, it is obvious that fire-balls, unless very large, would not be visible during the day. The observed number will therefore be greatest when the nights are longest; that is, when the earth is near its perihelion. This, it will be found, is precisely in accordance with observation.