260 The Temperature of Water 



and length that when the cup is introduced into the 

 cylindrical vessel, it remains firmly fixed in the axis of 

 it, and in such a situation that the bottom of the cup 

 is elevated just i^ inches above the bottom of the 

 cylindrical vessel. 



In the middle of this cup there stands a vertical tube 

 of thin sheet brass J of an inch in diameter and T \ of an 

 inch in length, open above, which serves as a support 

 for another smaller cup (C), which is made of cork, the 

 brim of which is on the same horizontal level with the 

 brim of the larger brass cup in which it is placed. 



This cork cup, which is spherical, being something 

 less than half of an hollow sphere, is I inch in diameter 

 at its brim, measured within, T 4 7 of an inch deep, and \ 

 of an inch in thickness. It is firmly attached to the ver- 

 tical tube on which it stands, by means of a cylindrical 

 foot \ of an inch in diameter and \ of an inch high, 

 which enters with friction into the opening of the vertical 

 tube. 



On one side of this cork cup there is a small opening, 

 which receives and in which is confined the lower ex- 

 tremity of the tube of a small mercurial thermometer 

 (D). The bulb of this thermometer, which is spheri- 

 cal, is T 3 -g- of an inch in diameter, and it is so fixed in 

 the middle of the cup, that its centre is \ of an inch 

 above the bottom of the cup ; consequently it does 

 not touch the cup. anywhere, nor does any part of it 

 project above the level of its brim. 



The tube of this thermometer, which is 6 inches in 

 length, has an elbow near its lower end at the distance 

 of i inch from its bulb, which elbow forms an angle 

 of about no degrees, and the thermometer is so fixed 

 in the cork cup, that the short branch of its tube, namely, 



