248 Of the Propagation of Heat 



which is open at one end, is closed at the other with a 

 hemispherical bottom, with its convex surface outwards. 

 The cylinder weighs 2261 grains, and the sheet-brass, of 

 which it is constructed, is 0.0128 of an inch in thickness. 



The bulb of the thermometer was placed in the lower 

 part of this brass cylindrical tube, and was confined in 

 the middle or axis of it by means of three pins of wood, 

 about -^^ of an inch in diameter, and \ of an inch long, 

 which pins are fixed in tubes of thin sheet-brass -^^ of an 

 inch in diameter, and 2V of an inch in length. These short 

 tubes, which are placed at proper distances on the inside 

 of the large brass tube at its lower end, and firmly at- 

 tached to it by solder, serve as sockets into which the 

 ends of the wooden pins are fixed, which, pointing in- 

 wards or towards the axis of the large cylindrical tube, 

 serve to confine the lower end of the bulb of the ther- 

 mometer in its proper place. Its upper end is kept in 

 its place, or the axis of the thermometer is made to co- 

 incide with the axis of the brass cylinder, by causing the 

 tube of the thermometer to pass through a hole in the 

 middle of a cork stopper which closes the end of the cyl- 

 inder. 



The bottom of the bulb of the thermometer does not 

 repose on the hemispherical bottom of the brass cylin- 

 der, but is supported at the distance of \ of an inch 

 above it, on the end of a wooden pin, like those just 

 described, which pin is fixed in a socket in the middle 

 of the bottom of the cylindrical tube and projects up- 

 wards. The ends of all these wooden pins which pro- 

 ject beyond the sockets in which they are fixed are reduced 

 to a blunt point. This was done to reduce as much as 

 possible the points of contact between the ends of these 

 pins and the bulb of the thermometer. 



