288 NOTES ON THE FLORA OF HAMILTON. 



The Higli School meteorological observations, on wMcli the follow- 

 ing comparison is based, have been" generally supposed not to be 

 reliable. The results of my comparison, however, agree remarkably 

 with a priori inferences. It is true, of course, that the observations 

 taken during a period of eight years form an insufficient basis for 

 determining the absolute climatic position of any place; but for 

 the purpose of developing the relations of the climates of two places 

 lying so near each other they are probably quite sufficient. The mean 

 annual temperature of Belleville is 43'98° F.; of Hamilton, 45'95°. 

 The mean temperature of the six winter months included between 

 September 30th and April 1st is, at Belleville 2 7 '87°, at Hamilton 

 31 '09°. The mean summer temperature of Belleville is 60-12°, of 

 Hamilton, 60 '73°. Thus, though the mean annual temperature' of 

 Hamilton is two degrees higher than that of Belleville, it is only 

 about half a degree warmer in summer, and over three degrees 

 warmer in winter than the latter place. These results, of course, find 

 their explanation in the greater proximity of Hamilton to the large 

 inland seas. At Belleville, the months of May and June are warmer 

 than the same months at Hamilton, but the remaining ten months 

 are colder. Water becomes heated more slowly than land, and con- 

 sequently the heat which raises the temperature of the Belleville 

 spring is abstracted at Hamilton by the neighbouring bodies of water. 

 The annual precipitation is about an inch less at Belleville, the means 

 being 35*53 and 36-76 inches respectively. The mean greatest cold 

 is, at Belleville 18-3°, and at Hamilton 13-7° below zero, which gives 

 about the difference that might be anticipated. Strange to say, 

 however, the next- result, which is determined by the same thermo- 

 meters that record the greatest cold, is at variance with a 2)riori con- 

 clusions. The mean period during which the minimu.m thermometer 

 does not mark below 32° F. is, at Belleville 161;|, at Hamilton only 

 151| days. As the shelter under which a mirdmum thermometer 

 must be kept to some extent retards radiation, so that slight frosts 

 are experienced in the open fields before it indicates frost,' I huye 

 made another calculation allowing 4° F. for the difference between 

 a thermometer protected from the rain, and one sub Jove frigiclo. 

 The mean period during which the minimuiu thermometer does not 

 fall below 36° F., and during which, consequently, there cannot be 

 the slightest frost, is, at Belleville 1361, at Hamilton 123f days. 

 Were it not that the minimum thermometers apparently record the 



