COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 by Alexander von Humboldt
Translated by E C Otte
from the 1858 Harper & Brothers edition of Cosmos, volume 1 —————————————————————————
From comets I would pass to the consideration of a far more enigmatical class of agglomerated matter — the smallest of all asteroids, to which we apply the name 'aërolites', or 'meteoric stones',* when they reach our atmosphere in a fragmentary condition.
[footnote] * (Much valuable information may be obtained regarding the origin and composition of aërolites or meteoric stones in Memoirs on the subject, by Baumbeer and other writers, in the numbers of Poggendorf's 'Annalen', from 1845 to the present time.) — Tr.
If I should seem to dwell on the specific enumeration of these bodies, and of comets, longer than the general nature of this work might warrant, I have not done so undesignedly. The diversity existing in the individual characteristics of comets has already been noticed. The imperfect knowledge we possess of their physical character renders it p 112 diifficult in a work like the present, to give the proper degree of circumstantiality to the phenomena, which, although of frequent recurrence, have been observed with such various degrees of accuracy, or to separate the necessary from the accidental. It is only with respect to measurements and computations that the astronomy of comets has made any marked advancement, and, consequently, a scientific consideration of these bodies must be limited to a specification of the differences of physiognomy and conformation in the nucleus and tail, the instances of great approximation to other cosmical bodies, and of the extremes in the length of their orbits and in their periods of revolution. A faithful delineation of these phenomena, as well as of those which we proceed to consider, can only be given by sketching individual features with the animated circumstantiality of reality.
Shooting stars, fire-balls, and meteoric stones are, with great probability, regarded as small bodies moving with planetary velocity, and revolving in obedience to the laws of general gravity in conic sections round the Sun. When these masses meet the Earth in their course, and are attracted by it, they enter within the limits of our atmosphere in a luminous condition, and frequently let fall more or less strongly heated stony fragments, covered with a shining black crust. When we enter into a careful investigation of the facts observed at those epochs when showers of shooting stars fell periodically in Cumana in 1799, and in North America during the years 1833 and 1834, we shall find that 'fire-balls' can not be considered separately from shooting stars. Both these phenomena are frequently not only simultaneous and blended together, but they likewise are often found to merge into one another, the one phenomenon gradually assuming the character of the other alike with respect to the size of their disks, the emanation of sparks, and the velocities of their motion. Although exploding smoking luminous fire-balls are sometimes seen, even in the brightness of tropical daylight,* equaling in size the apparent p 113 diameter of the Moon, innumerable quantities of shooting stars have, on the other hand, been observed to fall in forms of such extremely small dimensions that they appear only as moving points or 'phosphorescent lines.'**
[footnote] *A friend of mine, much accustomed to exact trigonometrical measurements, was in the year 1788 at Popayan, a city which is 2 degrees 26' north latitude, lying at an elevation of 5583 feet above the level of the sea, and at noon, when the sun was shining brightly in a cloudless sky, saw his room lighted up by a fire-ball. He had his back to the window at the time, and on turning round, perceived that great part of the path traversed by the fire-ball was still illuminated by the brightest radiance. Different nations have had the most various terms to express these phenomena: The Germans use the word 'Sternschnuppe', literally 'star snuff' — an expression well suited to the physical views of the vulgar in former times, according to which, the lights in the firmament were said to undergo a process of 'snuffing' or cleaning; and other nations generally adopt a term expressive of a 'shot' or 'fall' of stars, as the Swedish 'stjernifall', the Italian 'stella cadente', and the English 'star shoot.' In the woody district of the Orinoco, on the dreary banks of the Cassiquiare, I heard the natives in the Mission of Vasiva use terms still more inelegant than the German 'star snuff.' ('Relation Historique du Voy. aux Régions Equinox.', t. ii., p. 513.) These same tribes term the pearly drops of dew which cover the beautiful leaves of the heliconia 'star spit.' In the Lithuanian mythology, the imagination of the people has embodied its ideas of the nature and signification of falling stars under nobler and more graceful symbols. The Parcæ, 'Werpeja', weave in heaven for the new-born child its thread of fate, attaching each separate thread to a star. When death approaches the person, the thread is rent, and the star wanes and sinks to the earth. Jacob Grimm, 'Deutsche Mythologie', 1843, s. 685.
[footnote] ** According to the testimony of Professor Denison Olmsted, of Yale College, New Haven, Connecticut. (See Poggend., 'Annalen der Physik', bd. xxx., s. 194.) Kepler, who excluded fire-balls and shooting stars from the domain of astronomy, because they were, according to his views, "meteors arising from the exhalations of the earth, and blending with the higher ether," expresses himself, however, generally with much caution. He says: "Stellæ cadentes sunt materia viscida inflammata. Earum aliquæ inter cadendum absumuntur, aliquæ verè in terram cadunt, pondere suo tractæ. Nec est dissimile vero, quasdam conglobatas esse ex materia fæculentâ, in ipsam auram ætheream immixta: exque aëtheris regione, tractu rectilineo, per aërem trajicere, ceu minutos competas, occultâ causa motus utrorumque." — Kepler, 'Epit. Astron. Copernicanæ', t. i., p. 80.
It still remains undertermined whether the many luminous bodies that shoot across the sky may not vary in their nature. On my return from the equinoctial zones, I was impressed with an idea that in the torrid regions of the tropics I had more frequently than in our colder latitudes seen shooting stars fall as if from a height of twelve or fifteen thousand feet; that they were of brighter colors, and left a more brilliant line of light in their track; but this impression was no doubt owing to the greater transparency of the tropical atmosphere*, which enables the eye to penetrate further into distance.