Abstract
THE calculations presented by Père Secchi, in his work “Le Soleil,” relative to solar temperature and solar radiation, tending to discredit the result of recent investigations on the subject, I have carefully examined the “solar intensity apparatus,” the indications of which form the basis of those calculations. This unique device will be found delineated on p. 267 of the work referred to, the accompanying illustration (Fig.I) being a fac-simile of the same. It represents a longitudinal section through the centre line, thus described:—A B and C D are two concentric cylinders soldered one to the other; they form a kind of boiler, the annular space being filled with water or oil at any temperature. A thermometer, t, passes through a tube, across the annular space, to the axis of the cylinder; it receives the solar rays introduced through a diaphragm, m n, the opening, o, of which is very little larger than the bulb of the thermometer. A thick glass, V, closes the back part of the instrument, and admits of ascertaining whether the thermometer is placed in a direct line with the pencil of rays. The interior cylinder and the thermometer t are coated with lamp black. A second thermometer, t', shows the temperature of the annular space, and consequently that of the inclosure. The whole apparatus is mounted on a support having a parallactic movement, to facilitate following the diurnal motion of the sun. The apparatus being exposed to the sun, it will be found, on observing the two thermometers, that their difference of temperature increases gradually, and that in a short time it ends by being constant.
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ERICSSON, J. Solar Heat . Nature 5, 344–347 (1872). https://doi.org/10.1038/005344a0
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DOI: https://doi.org/10.1038/005344a0