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
"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
Transactions of the American Philosophical Society,vol. 6