lO THE ATTAINMENT OF VERY LOW TEMPERATURES 



expected, the efificiency decreases slightly in proportion as the mass- 

 flow of the air increases. The temperature measurements indicate, 

 however, that the gradient in the lower part of the coil is practically 

 independent of the quantity of air passing through it, though the tem- 

 perature difference at the exit became slightly greater. Bradley and 

 Rowe (he. cit.) arrive at a similar result. 



IV. Application of These Results to the Construction of a 

 New Air Liquefier. 



The result of these experiments seemed to show that the introduc- 

 tion of the vulcanized fibre discs increases the rate of heat interchange 

 in the upper part of the coil, where the temperature difference between 

 the two streams of gas is comparatively small, but is non-effective so 

 far as the lower third at least is concerned. 



The lower part of the liquefier which I constructed is arranged as 

 in figure 3, but in place of the cap there is a metal cylinder filled with 

 a coil constructed of two pipes coaxially. This part of the coil is 25 

 centimetres long and 10 centimetres in diameter. The cylinder enclos- 

 ing it is secured to the vacuum vessel by means of a rubber sleeve, and 

 is enclosed in a wooden casing filled with animal wool. 



The results obtained with it have been quite satisfactory. The 

 temperature difference at the inlet and outlet is smaller than can be 

 measured, and the yield of liquid air is, within the limits of experi- 

 mental error, as high as has been obtained with any liquefier. 



Table II. Result of Experiment with New Air Liquefier. 



V. The Effect of Initial Pressure on the Efficiency of a 



Liquefier. 

 I had intended to carry out experiments with a view to investigat- 

 ing the process from this point of view if results had not already been 



Table III. Bradley and Rowe Eperiments. 



^Bradley and Rowe {loc. cit.) find 0.047 per atmosphere for their liquefier. 

 The difference is well within the limits of experimental error. 



