22 



ROYAL SOCIETY OF CANADA 



tained, including night readings, which will, it is hoped, throw consider- 

 able light on river ice formation. 



Il is to be regretted that the extreme weather which was experienced 

 the winter before, could not have been repeated, as owing to the mildness 

 of the winter, the air did not fall more than 10° below zero F. during 

 the entire time of the experiments. A great many readings have been 

 obtained on what may be termed " zero" days, when the temperature was a 

 few degrees either way from 0° F. Observations have also been taken in 

 stormy, cloud}^ and bright weather, showing that all these conditions 

 have an important influence in determining the temperature of the open 

 water. 



Details of the Observations. 



The amount which the open river may become cooled below the 

 freezing point appears to be of the same order as under the surface ice, 

 but the extent to which it may be warmed by sun and rain is much larger 

 than could be expected under a surface sheet. 



Many observations were destroyed during the taking owing to want 

 of propel' laboratory conditions, and were never recorded, while others 

 had to be discarded from the same cause, even after the woik had been 

 completed. The following table will, however, give a few of the observed 

 differences on various dates, worked out to the ten-thousandth place. 

 The writer feels confident that they were measured under as steady and 

 uniform conditions as was possible to produce in the observation shanty, 

 and necessary to maintain for an accuracy of one-thousandth of a degree : 



Date. 



Feb. 3rd. 



" 5th. 



" 7th. 



" 8th. 



" nth. 



" 12th. 



" 13th. 



" 15th. 



March 1st. 



Air Temp. 

 Fahrenheit. 



Max. 



+ 20° 

 + 32° 



+ 38° 

 + 34° 



+ 18' 



+ ir 



+ 17° 

 + 33 = 



+ 22' 



Min. 



Sunshine 

 in percent 

 of possible. 



+ 10° 



— 3° 

 + 27" 

 + 28° 



— 3° 



— 2° 

 0° 



+ 24° 



— 10° 



89 

 88 

 00 

 00 

 94 

 00 

 100 

 G7 



25 



DifF. from Freezing Point 

 in Degree Centigrade. 



Current. 



Quiet Water. 



0000 



+ 00197° 

 + 0-0547° 

 + 00137° 

 — 00005° 



+ 00280° 



+ 0215° 

 + 00182° 

 + 0-0415° 

 + 0- 01.51 

 - 00068° 

 + 00186° 

 + 0-0423° 



0-0000 



The records of sunshine and velocity of wind are taken from the 

 monthly reports of the McGill College meteorological observatory. Most 



