An Experimental Inquiry Into the Nature and Propagation of Heat (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER II. TN a close room without a f1re, place the tin reflector near the end of the table, (See f1g. 1.) and set the canister on its stand a few feet distant, and with its papered or blackened side directly fronting the reflector; and having, by means of a lighted taper or otherwise, found the place of the corresponding focus, move to that spot the ball of the differential thermometer containing the coloured liquor, which, to avoid circumlocution, I shall in future term the textit{focal ball, and bring the plane of the instrument parallel to the face of the reflector. Things being in this state of preparation, f1ll the canister with boiling water, and adapt the cap with its thermometer. The coloured liquor of the differential thermometer will be perceived immediately to rise; in the space of The figure represents a screen in front of the canister, but. which is introduced only in the e1penments related in the neit chapter. two or three minutes it will have mounted the top of the scale, arrd, having remained a short while stationary, it will afterwards slowly descend in proportion as the canister cools. I used commonly the six-inch canister, placed at the distance of three feet from the deep reflector; and, under such circumstances, the effect produced on the tbcal ball amounted at its highest range to about 80 degrees. But after many trials, I found this effect, in every possible case, to be exactly proportioned to the heat of the canister, or the difference of its temperature from that of the room: an observation which, by introducing such simplicity, very much facilitated the prosecution of the experiments. The thermometer generally indicated 95 degrees centigrade, when I began to note the effect on the focal ball; and I continued at proper intervals to register ...