182 Lord Eayleigh. [Sept. 1, 



immersed in liquid air, is in the form of a vertical tube, 2J cm. in 

 diameter and 22 cm. long, closed below and above connected laterally 

 to the main channel. 



The first experiment on July 13 was upon gas from the top of the 

 bottle as supplied, and without treatment by liquid air, with the view 

 of finding out the worst. The weight was 3-6015, about 35 milli- 

 grammes too light. The stock of material was then purified, much as 

 in 1896. For this purpose the bottle was cooled in ice and salt* and 

 allowed during about one hour to blow off half its contents, being 

 subjected to violent shaking at frequent intervals. Subsequently three 

 weighings were carried out with gas drawn from the bottom, but 

 without treatment by liquid air. The results stand : 



July 18 3-6368 



July 20 3-6360 



July 25 3-6362 



Mean 3-63633 



Next followed experiments in which gas, still drawn from the 

 bottom of the bottle, was further purified by condensation with liquid 

 air. The gas, arriving in a regular stream, was solidified in the 

 condensing chamber. When it was judged that a sufficiency had been 

 collected, the tap behind was turned and a high vacuum established 

 over the solid mass with the aid of the Topler pump. The pump 

 would then be cut off and the gas allowed to evaporate and accumulate 

 in the globe. A reapplication of liquid air caused the gas to desert 

 the globe for the condensing chamber, until in a surprisingly short time 

 a vacuum was re-established. Little or nothing could now be drawn 

 off by the pump, and it was thought that a distinct difference could be 

 perceived between the first and second operations, indicating that in 

 the first condensation a little impurity remained gaseous. If desired, 

 the condensation could be repeated a third time. On one occasion 

 (August 7) the condensed gas was allowed to liquefy, for which purpose 

 the pressure must rise to not far short of atmospheric, and to blow off 

 part of its contents : 



August 1 3-6363 



Augusts 3-6367 



August 7 3-6366 



Mean 3*63653 



The treatment with liquid air raised the weight by only 0'2 milli- 

 gramme, but the improvement is probably real. That the stock in 



* The lower the temperature below the critical point, the more effective is this 

 procedure likely to be. 



