4io Of the Propagation of Heat 



ment maker to the Academy, by whom I was assisted in 

 making them. 



Finding the construction of the instrument made use 

 of in these experiments attended with much trouble and 

 risk, on account of the difficulty of soldering the glass 

 ball to the tube of the thermometer without at the same 

 time either closing up, or otherwise injuring, the bore 

 of the tube, I had recourse to another contrivance much 

 more commodious, and much easier in the execution. 



At the end of a glass tube or cylinder about eleven 

 inches in length, and near three quarters of an inch in 

 diameter internally, I caused a hollow globe to be blown 

 \\ inch in diameter, with an opening in the bottom 

 of it corresponding with the bore of the tube, and 

 equal to it in diameter, leaving to the opening a 

 neck or short tube, about an inch in length. Having a 

 thermometer prepared, whose bulb was just half an inch 

 in diameter, and whose freezing point fell at about 2f 

 inches above its bulb, I graduated its tube according to 

 Reaumur's scale, beginning at o, and marking that 

 point, and also every tenth degree above it to 80, with 

 threads of fine silk bound round it, which being moist- 

 ened with lac varnish adhered firmly to the tube. This 

 thermometer I introduced into the glass cylinder and 

 globe just described, by the opening in the bottom of 

 the globe, having first choaked the cylinder at about 2 

 inches from its junction with the globe by heating it, 

 and crowding its sides inwards towards its axis, leaving 

 only an opening sufficient to. admit the tube of the ther- 

 mometer. The thermometer being introduced into the 

 cylinder in such a manner that the center of its bulb 

 coincided with the center of the globe, I marked a place 

 in the cylinder, about three quarters of an inch above 



