By arrangement with the
Post Office, the astronomers at Greenwich despatch each morning a
signal from the observatory to London at ten o'clock precisely. By
special apparatus, this signal is thence distributed automatically
over the country, so as to enable the time to be known everywhere
accurately to a single second. It was part of the same system that a
time ball should be dropped daily at one o'clock at Deal, as well as
at other places, for the purpose of enabling ship's chronometers to
be regulated.
Airy's writings were most voluminous, and no fewer than forty-eight
memoirs by him are mentioned in the "Catalogue of Scientific
Memoirs," published by the Royal Society up to the year 1873, and
this only included ten years out of an entire life of most
extraordinary activity. Many other subjects besides those of a
purely scientific character from time to time engaged his attention.
He wrote, for instance, a very interesting treatise on the Roman
invasion of Britain, especially with a view of determining the port
from which Caesar set forth from Gaul, and the point at which he
landed on the British coast. Airy was doubtless led to this
investigation by his study of the tidal phenomena in the Straits of
Dover. Perhaps the Astronomer Royal is best known to the general
reading public by his excellent lectures on astronomy, delivered at
the Ipswich Museum in 1848.
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