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A view of the theories which have been proposed to explain the origin of meteoric stones. By Jeremiah Day, Professor of Mathematics and Natural Philosophy in Tale College. (From the Memoirs of the Connecticut Academy of Arts and Sciences, vol, i. Part 1.*)
THIS paper gives a clear statement of the principal facts and opinions, and combats with much force and fairness the commonly received theories, relating to the phenomena of meteoric
That stones of a peculiar character have fallen to the earth from great heights, and that they have proceeded from a meteor-like appearance in the air, seems no longer to be denied or doubted A luminous body of considerable magnitude and splendor ap pears in the atmosphere, moving with great velocity; on a sudden it bursts with a loud explosion, and a number of fragments descend toward the earth with a hissing noise, as of a rugged body passing rapidly through the air, something is heard to strike the ground in different places, search is made, the ground appears to have been recently broken and turned up, and at some depth hard semi-metallic masses, unlike any thing else in the neighbourhood, yet exactly agreeing among themselves, are found, in a heated state, and bearing evident marks of fusion; nay more, these stones are found lodged upon straw and light substances they have penetrated the roofs of buildings, and killed animals that happened to be in their way--they have been in some instances followed by the eye, and actually seen to strike the ground at the distance of only a few yards from the observer. All this is attested by many witnesses at different times, and in different quarters of the world. This mass of evidence taken together is absolutely irresistible. The light then that is emitted, the explosion that is heard, and the stones that have fallen, are all parts of the same phenomenon.¿.
It was our intention to have given a review of the whole of the first part of this volume; but the length to which it would have extended prevents its insertion in the present number,
But sometimes the fall of stones is not known to take place, when all the other circumstances are essentially the same; a luminous object of a similar form and size, moving at a like rate, and at about the same height, and separating and disappearing in a similar manner, and followed by a similar report. Shall we not conclude then that this is a phenomenon of the same general class, especially as it is possible, that stones may have fallen in these cases, in such places as did not admit of their being observed, or that the substance of the stones may have been in some instances reduced to powder by the explosion, and diffused through the air.
There are other appearances also which fail of being accompanied with any audible sound, though alike in every thing else; this is still easier to account for. It may have been too distant
the actual report may have been less violent. Again, these bodies differ very much in their form, and size, and splendor. Though generally round, some are observed to be spheroidal, some oblong like an arm, with a knob at one end, some conical, and various other shapes. Some also are, to appearance, as large as the moon, and even much larger, while others are smaller, and of all sizes intermediate between that of the moon and a large star. That they should differ in brilliancy and quantity of light is a natural consequence of their different distances and altitudes. Indeed, all these varieties and defective. circumstances may be explained in perfect consistency with their general character. They agree remarkably in all those points, which seem to determine their nature-they are always seen in or near our atmosphere-they appear but for a short time-their motion is inconceivably rapid, in a direction nearly parallel to the horizon-they emit light independently of the And it is remarkable to observe, how those common occurrences, called shooting stars, resemble the larger meteors in several other particulars. They appear suddenly, and are suddenly extinguished, and often with the evident marks of an explosion, small sparks being seen to fly off, and smoke remaining behind, and sometimes indeed a faint sound has been heard, which was supposed to proceed from that explosion. And indeed the principal difference observed, variety of magnitude and splen
dor, is more apparent and imposing than real and characterisstic. It is just what we note in other bodies, comets for instance, which are notwithstanding considered as belonging to the same class. Nay, it is just what ought to take place, and what is a necessary consequence of a diversity of magnitude or distance, and a variety of elevation, and of course difference of density in the medium, whence the light is supposed to be derived. It is then perhaps most reasonable to conclude, that those meteors which are attended with the fall of stones, and those which are defective as far as we know in this particular, and those small objects that are flying across our sky in great numbers every night, are all phenomena of the same kind, and are to be explained in the same way. In the examination of the theories which have been proposed, it may be proper to consider them with reference to all this variety of character, and frequency of occurrence.*
• The very great resemblance among these meteors becomes more striking when we compare them with those curious appearances called ignes fatui, wills with a wisp, and Jacks with a lanthorn. These are seen more frequently in rainy and snowy weather, and in damp places, and generally about six feet from the ground. They appear to have no heat, as the places they frequent, though containing combustible materials, are never found to exhibit any marks of fire. They continue for a long time, and though they are in motion, their motion is various and uncertain, as if produced by the agita. tion of the air. Some appear as large as a common candle, others give as much light as a torch. They resemble both in light and color a flame, strong enough to reflect lustre on surrounding objects. They change their size and figure, sometimes spreading themselves pretty wide, and then contracting again; sometimes they appear to break into two, and then meet again; sometimes they float like waves, letting drop sparks of fire; sometimes they disappear suddenly, and appear again in another place. It is thought by some that they are made to flee before one by the motion of the air. Sir Thomas Dereham, seeing one in a calm, clear, dark night, with gentle approaches, got up within two or three yards of it, and viewed it with all possible care. He found it frisking about a dead thistle, standing in the field, till a small motion of the air made it skip to another place, and thence to another. He was satisfied that it was not the glows .worm. In Italy the country people call them cularsi—perhaps from a fancied similitude to those birds, and because they consider them as birds, the belly and other parts of which are resplendent, like our shining flies. Their light has been supposed by some to be derived from inflammable air, set on fire by electricity; by others to be of a phosphoric nature. Some
Before following Mr. Day in his examination of hypothe ses, we shall state a few general facts, and recite a few particular cases, in order that we may be better prepared to judge of the attempts that have been made to explain them.
It seems to be well ascertained that these phenomena are restricted to no region of the earth, to no season of the year, to no time of the day, and in their course to no point of the compass. It has been remarked, however, that they have gen erally occurred in fair weather, when there have been few clouds
of their phenomena are not very easy to be explained on either supposition. A very accurate and skilful observer of natural appearances, during the month of March, as he approached a river near Bologna, perceived a light, which shone very strongly on some stones that lay on the banks. "It seemed to be about two feet above the stones, and not far from the water of the river: in figure and size it had the appearance of a parallelo. piped, somewhat above a Bolognese foot in length, and about half a foot high, its longest side laying parallel to the horizon: its light was very strong, insomuch that he could very plainly distinguish by it part of a neighbouring hedge, and the water in the river. The gentleman's curiosity tempted him to examine it a little nearer; in order to which, he advanced gently towards the place, but was surprised to find, that insensibly it changed from a bright red to a yellowish, and then to a pale colour, in proportion as he drew nearer, and that when he came to the place itself, it was quite vanished. On this he stepped back, and not only saw it again, but found that the farther he went from it, the stronger and brighter it grew; nor could he, on narrowly viewing the place where this fiery appear ance was, perceive the least blackness, or smell, or any mark of an actual fire. The same observation was confirmed by another gentleman, who fre quently travels that way, and who asserted, that he had seen the very same light five or six different times, in Spring and Autumn, and that he had atways observed it in the very same shape and the same place; which seems very difficult to be accounted for. He said further, that once he took par ticular notice of its coming out of a neighbouring place, and then settling itself into the figure above described." Phil. Trans. Abr. vol. vii. p. 374, &c.
The common meteors, called fireballs, shooting stars, &c. appear to be sufficiently distinct from the northern lights, although there is a rustling noise sometimes observed attending both, and not very unlike. Bergman makes the average height of the northern lights, upon a mean of thirty computátions, to be about four hundred and fifty miles English. It is remarkable however that a large portion of these meteors appear to come from the north. The ancients also describe them as coming more frequently from this quarter. “Ideo cirea septentrionem frequentissimè apparent quia illic «plurimum est æris pigri." Senec. Quæst. Nat. lib. vii. -
and little or no wind. We recollect no exception. They are generally of a globular form, often pretty well defined, of all apparent dimensions and degrees of brilliancy less than those of the moon, and sometimes even compared to the sun in point of light. They are often surrounded with scintillations, and followed by a train of various lengths. They appear to move with great rapidity, and generally in a continued curve nearly horizontal, but inclined a little downward. They continue in sight but for a short time. Except in a few very rare instances of a duration of fifteen or twenty minutes, so far as we are acquainted, they have been seen at most for two or three minutes and generally for less than one. They are often observed through an extent of several hundred miles, and their altitudes have been computed to be from one to eighty or an hundred miles. This point is pretty well ascertained within certain limits, not only from the circumstance of their being seen at a considerable apparent altitude at places remote from each other, but these estimates are confirmed by observations that are made by different persons differently situated, of the interval that elapses between the appearance of an explosion, and the actual hearing of a report not otherwise to be accounted for. It is evident then, that the real magnitudes of these bodies must be very considerable, in some instances not less than two or three miles, and in all incomparably greater than any of those masses which have been known to reach the earth, or than all put together which in any case have been actually found or can be supposed to have fallen. It is evident also from the apparent velocity and the known distance, that the real velocity must be astonishingly great. In several instances that have been particularly attended to, it must have been not less than two or three miles in a second; that is, five or six times the greatest rate of a cannon ball; and in one or two remarkable cases it has been computed to be even ten or twelve times this quantity.*
We have collected, principally from the Philosophical Transactions, the following estimates of the duration, altitude, and velocity of different meteors. They were determined by different persons. Some may be depended upon as pretty near the truth, others are more uncertain.
Duration, in seconds 3, 10, 12, 25, 30, 60, nearly 60, one 15 minutes, and one 30 minutes.