so .ROYAL SOCIETY ON CANADA 



Liquid air, enclosed in a suitable vessel, was made to boil vigor- 

 ously, and the cooled air led directly by suitable tubes into the water, 

 and allowed to bubble through. The water experimented with was 

 enclosed in a glass vessel immersed in a freezing-point mixture of snow 

 and water, and cooled to zero. The liquid air was placed in another 

 vessel, through the bottom of which two glass tubes protruded. These 

 tubes passed from the space above the liquid air to the water below. 

 The chilled air was thus conveyed as directly as possible into the water. 

 In addition to the stirring produced by the rapid bubbling, a glass stirrer 

 v/as provided. The obvious advantages of this method over any means 

 of external cooling is that the ice that is formed is of the fine needle 

 variety, exactly similar in appearance to frazil, instead of a cake of ice 

 that, by the external method, would be formed around the sides of the 

 vessel. Some difficulty was encountered in the freezing of water in 

 the tubes conveying the chilled air, but with a strong blast this was of 

 small amount. In order to measure the small difference of tempera- 

 ture between the water in which ice was being formed, and a uniform 

 mixture of snow and water so protected as to be neither gaining nor 

 losing heat, a pair of differential platinum thermometers was used, 

 having a scale oai a suitable resistance box of ten centimetres to a degTce 

 centigrade. With a vernier it was possible to set the contact piece to 

 1/100 of a millimetre, and oteerve the deflections on a highly sensitive 

 galvanometer. It was therefore possible to measure to the 1/10,000 

 of a degree with comparative ease, and a difference of 1/100 produced a 

 large deflection. The differences which it was expected would be 

 observed were of the order of a few thousandths; it was therefore neces- 

 sary to pay particular attention to the readings. The method of 

 carrying out an experiment was such that direct observation of the dif- 

 ference was obtained. One reading was made with the two thermo- 

 meters in the snow mixture, and the second reading with one thermo- 

 meter in the snow mixture and the other in the water. 



It was possible to obtain at once a check of the ice point, by stopp- 

 ing the flow of chilled air, when the temperature of the water imme- 

 diately rose to. the zero point. In all cases this reading corresponded 

 with the reading when both thermometers were together in the snow 

 mixture. 



Preliminary measurements were made witih a Beckmann ther- 

 mometer graduated to hundredths and reading to thousandths. At the 

 outset, when the first ice crystals were forming, the temperature sank 

 over a hundredth below freezing, whidh was measural>le. but when 

 larger quantities of ice crystals were present the instrument was not 

 sensitive enough. 



