ABNORMAL VARIATIONS AT TORONTO. 117 



From table XVIII. , wherein the abnormal variations of the pressure 

 of dry air with their proper signs are arranged according to the 

 direction of the wind at the hour of observation, it is seen that the 

 sis:ns are the same as those for the barometer, excepting that the 

 pressure of dry air with a N. W. wind is decidedly above the normal 

 and with a South wind slightly below it. 



Tables XIX. and XX. give for each of the three years, 1860 to 1862, 

 and for each month on the average of the three years, the mean change 

 in the pressure of dry air during twenty-four hours. 



The average changes in the four quarters, together with those for 

 the barometer, both derived from the same three years are as follows : 



Spring. Summer. Autiimu. Winter. Year. 



Dry Air 0.228.... 0.207.... 0.237.... 0.302.... 0.243 



Barometer.. 0.197 .... 0.137 .... 0.192 .... 0.273 .... 0.199 



Hence while the diurnal change in the pressure of dry air varies 

 vdth the seasons in a manner similar to that of the barometer, the 

 change is considerably greater for the former. 



From table XXI it is seen that the pressure of dry air increases in 

 twenty-four hours with a resultant wind from N., N.W, and "W., and 

 decreases with a resultant from any other quarter. This is found to 

 be true for each month taken separately with eight exceptions only 

 out of the whole ninety-six. 



PRESSURE OF VAPOUR 



Tables XXII. and XXIII. give the abnormal variations of the 

 pressure of vapour in each of the three years and for each month on 

 the average of three years. The transition from month to month 

 is not quite regular. The greatest monthly mean digression is 0.099 

 in August, and the least, 0.040, occurs both in January and March. 

 The annual fluctuations in the average amount of the pressure of 

 vapour and in the extent of its abnormal variations, are very similar in 

 character, as may be seen from the .nnnexed table, by which also it 

 appears that the irregular variation averages about one-fourth of the 

 whole pressure of vapour. 



Spring. Summer. Autumn. Winter. Year- 



Pressureof Vapour 0.200 0.441 0.28.5 0.119 261 



Variation 0.055 0.090 0.071 0.043 ...0.065 



Table XXIV. shews that the maximum variation in the pressure of 

 vapour is at 2 p. m., and the m.inimum at 6 a. m., which are also the 



