Ml' Miller's Description of a new Pyrometer. 127 



ment I have more confidence than in my own, is new in its 

 application, and correct in theory ; but the practical utility 

 of this contrivance remains to be tested. The difficulty that 

 attends the invention of an instrument of this kind, that in 

 its use is submitted to the torture of fire, may be inferred 

 from the disagreements found in tables of temperatures above 

 the boiling of merCTiry. 



My aim has been to make the mercurial thermometer sub- 

 servient to the measurement of high heats. As in mecha- 

 nics, a comparatively small weight, placed on the lever of a 

 steelyard, counterpoises and determines the weight of the 

 load, it seemed also possible by some method to determine, 

 by the thermometer itself, temperatures beyond its range* 



With this view experiments were first tried with a short 

 cylinder of u'on, of one inch diameter, a tube of sheet-iron, 

 and a thermometer, proceeding as follows : — The iron cylin- 

 der, after being heated, was dropped into the tube ; the ther- 

 mometer, graduated on the stem, Avas suspended at a small 

 distance above it, and at the same distance in all expeiu- 

 ments, to receive the impression of radiated heat ; the rise 

 of the thermometer during a given time was observed. It 

 was supposed that the thermometer v/ould be aff'ected ac- 

 cording to the intensity ; — that if the iron heated to 100° 

 above the atmospheric temperature caused the thermometer 

 to rise 12" in four minutes, 200" would cause it to rise 24" 

 in the same time. 



The following improvement was made on this arrange- 

 ment. The thermometer was bent to a right angle about an 

 inch from the bulb, which was afterwards imbedded to the 

 depth of about half an inch in sand, contained in a metal 

 cupj; the thermometer stem was passed through a hole in the 

 side of the cup, and fixed in an upright position : a cylinder 

 of iron weighing about six ounces, with a thin handle, was 

 licated in mercury to various known degrees, and then ap- 

 plied to the shielded bulb. In each expei'iment, the degree 

 to which the thermometer rose during four minutes, was 

 noted, and the numbers passed over were counted. The re- 

 sults with moderate heats were tolerablv uniform ; an in- 



