Section III., 1904 [ 29 J Tkans. R. S. C. 



IV. — On the Artificial Production of Frazil Ice, together with Measure- 

 ments of the Temperature Conditions in the Water. 



By Howard T. Barnes, D.Sc, Assistant Professor of Physics, 

 McGill University. 



(Read June 23, 1904.) 



In the last communication ^ which the author made to this Society 

 or the subject of river ice formation, it was suggested that the tem- 

 perature of a mixture of ice and water was constant only where there 

 was neither a gain nor loss of heat. A diagram was shown to illustrate 

 the way in which the temperature possibly varied. Starting with 

 water at the freezing point, free from ice, an abstraction of heat causes 

 a fall of temperature. As ice forms the -iemperature depression de- 

 creases, the rate of abstraction of heat remaining constant. When the 

 quantity of ice becomes large the temperature falls again. Conversely, 

 starting with ice melting, the temperature rises above the freezing point, 

 falls again as the ice disappears, and then rises when the amount of ice 

 becomes small compared with the water. 



It was pointed out in support of this view that the temperature 

 measurements made on the St. Lawrence river by the author gave an 

 indication of the size of these deviations from the fixed point. These 

 differences were found to be of the order of a few thousandths of a 

 degree centigrade during the winter, when a considerable proportion 

 of ice was present in the water. It was stated in the paper before re- 

 ferred to that experiments were to be made in the laboratory to verify 

 these measurements. Greater difficulty was encountered in arranging 

 the conditions than was first anticipated. This arose chiefly from the 

 want of any suitable means of rapidly abstracting heat from the water, 

 at a constant rate, and, at the same time, have the ice that was formed 

 produced in fine needle crystals resembling in all respects the actual 

 river conditions. On account of the minute temperature differences 

 to be measured, great care had to be exercised in maintaining the purity 

 of the water and providing for efficient stirring. 



The obvious way was to pass a stream of cold air rapidly through 

 the water, but no method of precooling the blast proved effective. On 

 the introduction of the Hampson-Linde liquid air plant in the labor- 

 atory, however, a method at once suggested itself, and was put into 

 successful operation during the past winter. 



' Trans. Roy. Soc. Can., 1896, 1897 and 1899. 



