116 ABNORMAL VARIATIONS AT TORONTO. 



are 0.206 in spring, 0.126 in summer, 0.190 in autumn, and 0.270 in 

 winter. 



It has been found from the observations of 1854 to 1859 that on 

 the whole the barometric pressure passes from one condition to another 

 by gradations, of which those in which the pressure increases, are 

 nearly equal in num.ber and magnitude to those in which the pressure 

 decreases, the average magnitudes of the ascending and descending 

 changes being respectively 0.194 and 0.197. 



From table XIV. in which the mean changes in the barometer, with 

 their proper signs, between 6 a.m. and 6 a.m. on consecutive days, 

 are arranged according to the resultant direction of the wind during 

 the day, it is seen that in both series, the barometer rises, on the 

 average of the year, when the resultant wind is from N., N.W., 

 and W., and that it falls with a resultant wind from other quarters. 

 It has been also found from both series that these statements hold 

 true in nearly every month taken separately. 



A comparison in the signs in tables XI. and XTV. corresponding to 

 the several winds, brings out the fact that the same winds that accom- 

 pany a relatively high barometer are for the most part those that 

 accompany a fall, and that the winds that correspond to a low 

 barometer commonly accompany a rise. 



PRESSURE OF DRY AIR. 



Tables XV., XVI. and XVII. give for each year, each month, and 

 each hour respectively, the mean abnormal variations of what is com- 

 monly designated as the pressure of dry air. 



The following are the quarterly means of the abnormal variations 

 of the pressure of dry air, together with* those of barometric pressure, 

 both being derived from the years 1860 to 1862 : — 



Spring. Summer. Autumn. Winter. Tear- 



Dry Air... . 0.215.... 0.184.... 0.211.... 0.258.... 0.217 

 Barometer.. 0.191 .... 0.128 .... 0.175 .... 0.233 .... 0.183 



The maximum"and minimum are as follows : — 



Dry Air. Barometer. 



Maximum 0.282 in December. 0.257 in December. 



Minimum 0.167 in July. 0.114 in August. 



From table XVII. a very faint trace of a diurnal period, better 

 marked in summer than in winter, is observable, the mean digressions 

 being slightly less^^at 10 p.m. than at 6 a.m. and 2 p.m. 



