Properties of the Alloys of Iron and Aluminium. 133 



tube also prevented the circulation of air between the 

 surrounding atmosphere and the interior of the box, and the 

 consequent heating of the ring. The box containing the ring- 

 was placed in the centre of a thin -walled metal vessel V, which 

 was closed with a tightly-fitting bung through which the glass 

 tube Q- passed. The vessel V was of about a pint and a half 

 capacity, and was filled with ether, which was introduced 

 through the tube K. The vessel was connected with a water- 

 pump and manometer by means of another tube L. it was 

 thus possible, by the rapid evaporation of the ether, to cool the 



Fig. 7. 



ring below the temperature of the surrounding medium, and 



by regulating the evaporation to vary the temperature at will. 



The bung was covered with melted paraffin before commencing 



• • . -i ~ 



an experiment, to insure air-tightness. The vessel V was 



placed in the cooling medium M contained in the large stone 

 jar J, which rested on a thick pad of flannel. The whole 

 arrangement was surrounded with a quantity of cotton- 

 waste 0. The cooling medium used in these experiments 

 was either a mixture of ice and salt, or carbon-dioxide snow. 



