26 ROYAL SOCIETY OF CANADA 



enough, about this time the quiet water became wanner than the current 

 by "0033° C, shoAving a différence itself from the freezing-point of — 0022** 

 C. The question suggests itself, whether there was an}' natural cause 

 for this change, and the only answer seems to be, that there was some 

 possible check to radiation occurring in the atmospheric conditions to- 

 wards morning. As a matter of fact, as the light grew stronger, the con- 

 ditions were such as to suggest a dull day, although during the night the 

 sky had been perfectly clear. Heavy banks of clouds wore noticed, which 

 cleared away, however, as the day advanced. 



A great deal of fine ice was noticed coming down in the currents 

 all night, especially noticeable during the early morning when the water 

 was slightly undercooled. 



Attempts were made to obtain similar readings on a number of 

 other occasions, but owing to practical and experimental details occur- 

 ring to prevent, no other all-night readings could be obtained. 



The coldest day on which readings were obtained was on March 1st, 

 in the morning, when the air temperature went down to — 10° F. after a 

 few days of mild, rainy weather. Many of these readings were rendered 

 valueless by the fact that a block of ice coming down in the current so 

 bent the stem of the thermometer as to sever a wire in the fine platinum 

 coil. Enough has been recorded, however, to show that the temperature 

 of the river did not vary to any extent from the freezing-point, certainly 

 not more than has ah-eady been found. 



Later readings during March ai'c not given on account of experi- 

 mental difficulties. It may be said that up to the middle of that month, 

 when the readings were discontinued, the temperature of the river water 

 showed no larger variations from the freezing-point. It was always pos- 

 sible, by noting the conditions of the weather, to foretell, with considerable 

 exactness, the temperature of the water. 



General Considérations. 



The extreme steadiness of the temperature of the river, both in open 

 water and under the surface ice, is a matter of great interest. 



From theoretical reasoning it is impossible to imagine water cooled 

 much below the freezing-point. Under favourable laboi-atory conditions, 

 water, free from ice and dissolved air, has been brought to several degrees 

 below. On the introduction of the smallest crj'^stal of ice, however, the 

 whole mass comes to the freezing-point with the formation of ice. The 

 solution can no longer bo cooled below the fi'eezing-point while any water 

 remains. 



That the apparent isothermal change of ice into water, or water into 

 ice, is dependent on minute temperature differences in its mass has already 

 been claimed by some authorities ; and that the temperature of a mixture 



