328 



Scientific Proceedings, Royal Dublin Society. 



a stopcock, s, in the manner shown in the accompanying sketch. 

 Each U tube is immersed in a vessel of water ; on one side, 

 A, the water is at the temperature of the air, on the other, B, at 

 some higher temperature. The vessel of warm water is jacketed 

 with a tin cylinder, having an aperture furnished with a door, X, 

 wide enough to allow the readings to be taken. After the U 



tubes are half filled with the liquid whose expansion is to be deter- 

 mined, a difference of level in the liquid in the two limbs of each 

 U tube is produced by either aspirating or blowing into the cross 

 piece and closing the stopcock. As a matter of practice it is 

 better to diminish the air pressure so that the liquid in the U 

 tube is caused to stand as shown in the drawings. 



Specially constructed thermometers, T, T', with open scales 

 and long bulbs, give the temperature of the water in each vessel. 



