]
Others repeated the experiment several times between this time and
1856, with more or less success; but, so far as I know, the first
quantitative result was that obtained in 1856 by Piazzi Smyth during
his Teneriffe expedition. On the top of the mountain, at an elevation
of ten thousand feet, he found that the moon's rays affected his
thermopile to the same extent as a standard candle ten feet away.
Marie Davy has since shown that this corresponds to a heating effect
of about 1/1300 of a Centigrade degree.
The subject was resumed in 1868 by Lord Rosse in Ireland; and a long
series of observations, running through several years, was made by the
aid of his three-foot reflector (not the great _six_-foot instrument,
which is too unwieldy for such work). The results of his work have,
until very recently, been accepted as authoritative. It should be
mentioned that, at about the same time, observations were also made at
Paris by Marie Davy and Martin; but they are generally looked upon
merely as corroborative of Rosse's work, which was more elaborate and
extensive.
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