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Published online by Cambridge University Press: 17 January 2013
The experiments which I now submit to the Royal Society are repetitions of those I made many months ago, for the purpose of ascertaining the Specific Heats of the Gases. The importance of the subject so impressed my mind, that I determined to spare no pains in the prosecution of the inquiry, and therefore I willingly withheld my first experiments from the public eye, until, by a fresh series, I might present them with the greater confidence. The apparatus employed in these experiments was calculated to operate upon greater quantities of the Gases than the former one, and as every precaution which had been suggested was adopted, they have, perhaps, given even more decisive results than the last. The results themselves, however, are in every important particular exactly the same. It is also but justice to myself to state, that the conclusions which the former experiments led to, were exactly the reverse of what I had anticipated, and that they seemed at the time totally opposed to the doctrines of Black and Crawford, which I am still disposed to credit to a limited degree.
page 207 note * The apparatus which I found most convenient for exploding gases, is a modification of Dr Ure's syphon eudiometer. It consists of a hole bored in the solid bottom of a mercurial trough, representing an inverted syphon; one end of which opens into the part containing mercury, and the other through the edge of the trough to the open air. To the latter opening is cemented an open glass tube; and to the former a common graduated eudiometer is made to fit accurately. When this apparatus is used, the graduated tube is filled in the usual way, and applied to the opening communicating with the trough. Mercury is poured into the other tube, to the same height as that contained in the graduated one. The finger is then applied to the open tube, and the electric spark passed. After the explosion, more mercury is poured into the open tube, to the same height that it had risen in the eudiometer, after which the degrees are read off.