Aerolites to Meteorites

In 1802, Edward Howard read a paper in front of the Royal Society stating unequivocally that “certain stony and metalline substances have, at different periods, fallen on the earth.” This was the first time that scientists accepted the existence of meteorites, though they didn’t yet call them that because their origins were, as Howard said, “involved in complete obscurity”. And so began an exciting thirty-one year period of astronomical befuddlement and activity to resolve the situation.

The connection ’twixt the stones in the ground and meteors in the sky was not even fully established yet. It was known that meteors were very high and very fast because Edmond Halley, in 1714, had started a veritable flurry of 18th century calculations made from sightings. But their nature was so inexplicable, especially given their flat trajectory, that any suggested links or provenance were hard to defend. Only Ernst Chladni, in 1794, suggested that they were from outer space.

On 26th April 1803, however, there was a breakthrough. One week later, in a letter dated Bâton d’or (Wallflower Day), Floreal XI as it was in the Calendrier Républicain of France at the time, M. Marais of l’Aigle described that he had seen a fireball that had “hung over the meadow”. It was a meteor with a landed meteorite impact: three thousand stones were said to have fallen, the largest of which weighed about 17lb. The French Home Office dispatched 29 year old Jean Baptiste Biot to investigate, and his report confirmed what Howard had said only the year before, as well as linking the phenomenon of meteors to the stones on the ground.

Though the connection was slowly being made, the stones still didn’t have a distinct name because to do so meant evincing a theory of origin. The first such theoretically grounded name after the l’Aigle event was “meteoric stone”, the earliest use of which I find in a work of 1805: On a Meteoric Stone that fell in the Neighbourhood of Sigena, in Arragon, in 1773, by Professor Proust. Proust was French and the piece was translated. The next year, the French were using the word ‘aérolithe’, in a piece by Thénard called D’un aérolithe tombé dans l’arrondissement d’Alais. This harks to the theory that the stones were made in the atmosphere.

In 1809, a paper by B.G. Sage was translated to English from the original in the Journal de Physique, which contains quite possibly the first ever use of the English word ‘aerolite’ (antedating the 2nd ed. OED by some six years). Yet “meteoric stone” was used for decades past the introduction of the more compact ‘meteorite’, the earliest example of which I can find, antedating the OED again by six years, is from 1818. It’s a light passing mention in a letter from Henry Heuland to a Dr. Bostock, dated 22nd July: “The gentleman through whom I procured these opals, presented to me a very interesting meteorite, not yet described in any work”. The word was probably already current.

There were enough theories by 1810 to require summarisation. Jeremiah Day’s paper of that year called On the Origin of Meteoric Stones provided just such a summary, discussing four main theories: 1) that accretions of gas form in the upper atmosphere and then fall to the earth; 2) that volcanoes violently shoot the matter out; 3) that matter is ejected from the moon; and 4) that they are the falls of “Terrestrial Comets”. Day’s favourite theory is the latter one, that like the sun the earth has its own comets which bounce off of its atmosphere, but he says that it’s not without its difficulties.

The “Terrestrial Comets” theory did, however, stick around. An anonymous article in The Analectic Magazine from a1820 expresses a similar opinion: “This earth is attended not only by the moon, but by numerous satellites of very inferior and various dimensions from one foot to several miles in diameter.” It’s ironic that even though this same author wrote that “the old whim, that sun, moon and stars were made to shine for the exclusive benefit of such vermin as we are, is long since exploded”, the author’s geocentrism was perhaps their biggest hurdle of separation from the truth.

Day’s summary of the theories missed out the early electrical theory. As far back as June 1785, an anonymous writer in the Edinburgh Magazine stated that “the electric origin of meteors is deduced from their connection with the northern lights”. The reasons given are shoddy, including that large meteors consistently seem to come from “the north or north-west quarter of the heavens, and indeed to approach very nearly the present magnetical meridian”. If Day knew of the septentrional theory, it’s perhaps not surprising that he omitted it from his summary.

After Day’s summary, the falls kept occurring. One particularly interesting one within the period was the Chassigny meteorite of the 3rd October 1815. Though at the time it didn’t cause as much discussion as, say, the l’Aigle fall, it was later shown to be a unique find that is now thought to have come from Mars. Its mineral content was named Chassignite, and a second example of it called NWA 2737 was found in Morocco in August 2000.

The resolution of the origin of meteors did not come until the great Leonid meteor shower of 13th November 1833. Henry Smith Williams takes up the story in his History of Science from 1923: “in observing it Professor Denison Olmstead, of Yale, noted that all the stars of the shower appeared to come from a single centre or vanishing-point in the heavens, and that this centre shifted its position with the stars, and hence was not telluric. The full significance of this observation was at once recognized by astronomers; it demonstrated beyond all cavil the cosmical origin of the shooting-stars.”

Ernst Chladni, the German scientist regarded as a “Father of Meteoritics” being the first to suggest that meteors came from outer space, was honoured in 1993 by having the mineral Chladniite named after him. Chladni, who gave up law to become a physicist, was indeed remarkably prescient, having preceded even Guiseppe Piazzi’s discovery of the asteroid belt by seven years.

by Sean B. Palmer, 2007-04-03

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