390 



Profs. G-. D. Liveing and J. Dewar. On the 



A represents a vacuum- jacketed vessel, partly filled with liquid air, in 

 which a second vessel, B, was immersed. From the bottom of B a 

 tube, a, passed up through the rubber cork which closed A, and from 

 the top of B a second tube, b, passed through the cork and on to the 

 rest of the apparatus. Each of these tubes had a stopcock, m and n, 

 and the end of tube a was open to the air. A wider tube also 

 passed through the cork of A and led to an air-pump, whereby the 



Fig. 1. 



pressure above the liquid air in A was reduced, and the temperature 

 of the liquid reduced by the consequent evaporation. To keep the 

 inner vessel, B, covered with liquid, a fourth tube, r, passed through 

 the cork, and its lower end, furnished with a valve, which could be 

 opened and closed by the handle q, dipped into liquid air contained in 

 the vessel C. As the pressure above the liquid in A was less than 

 that of the atmosphere, on opening the valve p some of the liquid air 

 was forced through r into A by the pressure of the atmosphere, and in 

 this way the level of liquid in A maintained at the required height. 



Since B was maintained at the temperature of liquid air boiling at 

 reduced pressure the air it contained condensed on its sides, and when 

 the stopcock n was closed and m opened, more air passed in through 

 the open end of a, and was in turn condensed. In this way B could 

 be filled completely with liquid air, the whole of the most volatile gases 

 being retained in solution in the liquid. 



The tube, b, passing from the top of B, was connected with a three- 



