Don José Joaquin Ferrer and the eclipse of 16 June 1806


Astronomers became interested in learning how to measure time long before sailors. The majority of astronomic calculations, whether the position of the stars and planets or the study of repetitive phenomena such as eclipses or the passage of comets, necessitate an extremely precise temporal frame of reference. The earliest chronometric regulators were installed in observatories for this very reason, and astronomers' expertise became so great that they were entrusted with the task of testing chronometers to ascertain their quality. The prestigious competitions and observatory prizes, orchestrated and awarded from the 19th century onwards, also have their roots in this trend.

In Arnold's day, observatories were equipped with impressive longcase regulators, such as those designed by Thomas Tompion, George Graham and John Arnold himself.

However, the most interesting astronomic phenomena did not necessarily occur in the skies above the official observatories. Eclipses, for example, trace complex routes on the earth's surface and, in order to observe these precisely, it is preferable to go in pursuit of them, rather than to wait several hundred years for the phenomenon to materialize in precisely the right place.

Eventually, the development of marine chronometers and miniaturization of precision timepieces freed astronomers from the confines of their fine observatories, allowing them to travel the world. This is how chronometers embarked on a series of cross-country travels, with Arnold's creations among the first models to do so.

Astronomers were extremely fond of their precision timepieces, and did not hesitate to emphasize this in their logbooks or in accounts of their travels published after completing their expeditions. Here is a particularly informative example.

Don José Joaquin Ferrer was a high-flying Spanish astronomer. In 1780, the young man's ship, bound for Caracas, was seized by the British Royal Navy. He was taken to England, where he turned adversity to account and studied mathematics and astronomy. He subsequently returned to Spain before leaving for Peru, where he made his fortune. Returning to Cadiz, he joined a trading house, which allowed him to indulge his passion for astronomy and geography on countless business trips.

In 1799, he settled in the United States, where he joined the American Philosophical Society in Philadelphia and made a name for himself thanks to the perspicacity of his topographical observations. In June 1806, he had the good fortune to witness the famous and magnificent total eclipse of the sun, foretold by Tecumseh:

"On the 8th of June I embarked in a packet for Kinderhook south landing, which is 15 geographic miles south of Albany on the bank of the river Hudson, to observe the eclipse, taking for that purpose an excellent chronometer of Arnold, No. 63; a circle of reflection; and an achromatic telescope, constructed by Troughton according to particular directions."

The conditions were excellent, the sky cloudless and, for the first time, he described the solar corona, an immense halo of light surrounding the sun: "It has appeared to me, that the cause of the illumination of the moon, as noticed above, is the irradiation of the solar disk, and this observation may serve to give an idea of the extension of the luminous corona of the sun."

Afterwards, he spent time at the Royal Observatory in Greenwich before travelling to Paris, where he became a member of the Institute and befriended Laplace and Arago.

He died in Bilbao in 1818, and the world is indebted to him for determining the longitude of Cuba and measuring the moon's precise diameter.



Transactions of the American Philosophical Society,vol. 6 (Philadelphia, 1809).


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