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VI.—Researches on Radiant Heat. Second Series.

Published online by Cambridge University Press:  17 January 2013

Balfour Stewart
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Extract

1. The first part of this paper describes the following groups of experiments:—

Group I. On the effect which roughening the surface of a body produces upon its radiation.

II. On the nature of that heat which is radiated by rock-salt, at 212°F.

III. On the radiation of glass and mica, at high temperatures.

The second, or theoretical portion, of the paper, has reference to the law which connects the radiation of a particle with its temperature, and to Dulong and Petit's experiments on this subject.

There is also an addition of a later date than the rest of the paper on General Diathermancy.

Type
Transactions
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 22 , Issue 1 , 1861 , pp. 59 - 73
Copyright
Copyright © Royal Society of Edinburgh 1861

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References

page 59 note * In the experiments with roughened surfaces, only one of the surfaces of the substance was roughened, the other being left polished. In radiation experiments, therefore, the roughened surface was placed next the pile; while in transmission experiments, it was placed furthest from the pile.

page 66 note * Provostaye and Desains estimated the proportion of heat reflected by mercury to be 77 per cent. The radiation, being complementary to this, may be reckoned to be 23 per cent. nearly.

page 66 note † It would have been better to have tested, by means of a direct experiment, to what extent the difference between the proportional absorption or radiation of mica at 200° F. and at 400° F. would have been diminished by doubling the thickness of the plate; but unfortunately the plate of mica was so much cut up by being used as a window, as to be unfit for being formed into a double screen.

We see, however, from Art. 37, that while the difference between the proportional radiation of a plate of glass (thickness lmm ) at 100 C. and 390 C. is 9 per cent., the same difference for a plate of double the thickness is only 7 per cent., or 2 per cent. less. We may, therefore, without much risk of error, adopt this difference of 2 per cent. for the mica under experiment.