O THE ATTAINMENT OF VERY LOW TEMPERATURES 



wires from the thermo junctions, which are not shown in the figure, 

 passed through a paraffined cork in the vertical opening of H, while 

 a rubber tube connected with the horizontal opening led to a gas-meter, 

 by means of which the volume of air was measured. 



A brass reducing piece L and two rubber sleeves M and N con- 

 nected the cylindrical vessel B with the vessel P in which the liquid 

 air collected. The liquid ran directly from the nozzle of B into P, and 

 to allow of the escape of the gaseous air which resulted in the evapora- 

 tion of a little of the liquid, the pinchcock 6^ could, if necessary, be 

 opened from time to time. 



The temperature gradients in the two coils are shown on the curve 

 in figure 4. The curve a represents the gradient in the coil A, in which 

 the perforated vulcanized discs had been inserted, and the curve h the 

 gradient in the simple coil B. 



The result of this part of my experiments is interesting. It will 

 be observed that in the case of both coils the temperature gradient is 

 at first very steep, but curiously enough the effect of introducing the 

 fibre discs is, so far as the lower section of the coil is concerned, the 

 reverse of what was looked for, the temperature gradient is rendered 

 less steep, not more so. Over the upper section of the coil the fibre 

 discs produce the desired effect, with the result that as a whole the 

 coil A produces a slightly more effective heat interchange than the 

 coil B. 



The explanation of these facts is, I believe, as follows : Over the 

 lower section of the coil, where the rate of heat interchange is normally 

 very high, though the fibre discs may increase the eddying effect, they 

 also shield the coils from close contact with gas, and hence their total 

 effect is negative. Over the upper two-thirds of the coil, where the 

 rate of heat interchange is low, the shielding factor is insignificant com- 

 pared with the action of the discs in producing eddy motion, and the 

 efficiency of the coil is increased. 



Table I. Results of Experiments with Coils A and B. 



It is important to note that, as appears from Table I, the per- 

 centage of air liquefied, for quantities passing through the liquefier 

 which vary as 2 is to 3, shows but slight variation. As might be 



