5 ° 
Sir Benjamin Thompson's 
in diameter, and its tube, about 10 inches in length, was sus- 
pended in the axis of a cylindrical glass tube, about of an 
inch in diameter, ending with a globe 1-^ inch in diameter, 
in such a manner that the centre of the bulb of the thermome- 
ter occupied the centre of the globe ; and the space between 
the internal surface of the globe and the surface of the bulb of 
the thermometer being filled with the substance whose con- 
ducting power was to be determined, the instrument was 
heated in boiling water, and afterwards being plunged into a 
freezing mixture of pounded ice and water, the times of cooling 
were observed, and noted down. 
The tube of the thermometer was divided at every tenth de- 
gree from o°, or the point of freezing, to 8o°, that of boiling 
water, and these divisions being marked upon the tube with 
the point of a diamond, and the cylindrical tube being left 
empty, the height of the mercury in the tube of the thermo- 
meter was seen through it. 
The thermometer was confined in its place by means of a 
stopple of cork, about 1^ inch long, fitted to the mouth of the 
cylindrical tube, through the centre of which the end of the 
tube of the thermometer passed, and in which it was ce- 
mented. 
The operation of introducing into the globe the substances 
whose conducting powers are to be determined, is performed 
in the following manner ; the thermometer being taken out of 
the cylindrical tube, about two-thirds of the substance which 
is to be the subject of the experiment are introduced into the 
globe ; after which, the bulb of the thermometer is introduced 
a few inches into the cylinder ; and, after it, the remainder of 
the substance being placed round about the tube of the thermo- 
