ON THE METEOROLOGY OF TORONTO IN CANADA. 



S5'nopsis of the Annual Variations at Toronto. 



59 



January ... 

 February... 



March 



April 



May 



June 



July 



August . . , 

 September 

 October .., 

 November 

 December 



Temperature. Vapour pressure. Gaseous pressure, 



26-7 



25-6 Min. 



321 



41-6 



505 



61-3 



651 



65 



58-5 



43-3 



35-5 



27-3 



5-1 1 

 5-1 1 



Max. 



•132 



•123 Min. 



•146 



•186 



•241 



•399 



■443 



•486 Mas. 



•402 



•232 



•179 



•138 



29-454 



29-396 



29-501 Max. 



29-398 



29-324 



29-165 Min. 



29-194 



29-219 



29-232 



29-407 



29-413 



29-488 



The Plates which are annexed exhibit — Plate XXI. the Diurnal variation, 

 projected in curves, of the temperature, tension of vapour, gaseous pressure, 

 and force of the wind. In each case the whole variation, i. e. the diiference 

 between the highest and lowest observation in the twenty-four hours, has 

 been made equal to 1| inch, and the proportionate amount has been laid off 

 at each hour of observation : the scales are of course wholly arbitrary. 



Plate XXII. The Amiual variation, projected in curves, of the temperature, 

 tension of vapour, and gaseous pressure. The whole variation of each has 

 here also been made equal to 1§ inch, without reference to absolute values 

 or to the scales employed in projecting the diurnal variations. 



Plate XXIIl. represents, on a scale of four inches to one-tenth of an inch, the 

 diurnal variations of the barometer and gaseous pressure, projected in curves, 

 and connected at each observation hour by vertical lines proportioned to the 

 elastic force of the vapour. This Plate is illustrative of the conversion of the 

 single progression of the gaseous pressure, into the double progression oi 

 the barometric pressure, by the presence and influence of the vapour pressure. 

 The detached curve is that of the diurnal march of the temperature, and is 

 inverted, for the purpose of shoAviug more distinctly its correspondence with 

 the curve of gaseous pressure. 



An inference of much practical utility to general observers may be drawn 

 from meteorological observations, made with the frequency which can only 

 be expected at those observatories, where a sufficient establishment is main- 

 tained for the express purpose of observation. We may find that compara/- 

 tively a very few observations in each day, at hours not inconvenient in ordi- 

 nary life, may furnish a very close approximation to the mean values and to the 

 annual and diurnal march of the atmospherical phsenomena. Thus from the 

 complete record at Toronto we find, as shown in the subjoined table, that the 

 mean values of the temperature, of the vapour tension and of the humidity, of 

 the pressure of the gaseous atmosphere, and of the whole atmospheric pressure, 

 may all be obtained, with a very near approximation, by a single observation 

 at 8 P.M. (mean time), providcsd the observation be made with tolerable pre- 

 cision in regard to the hour. By combining with this an observation about 

 sunrise, and another between 2 and 4 in the afternoon, the maximum and 

 minimum of the temperature, of the aqueous and gaseous pressure, and of 

 the humidity, may also be obtained. These hours are by no means inconve- 

 nient for persons whose avocations permit them to keep a register at all ; 

 and appear in every way preferable to a selection which makes 3 o'clock in 

 the morning one of the observation hours. That hour is perhaps the most 

 generally inconvenient for the purpose of the whole twenty-four. The hours 

 here suggested must not however be understood to be of universal applica- 

 tion : they are not so thoroughly suitable, for example, at stations where, as 

 at Trevandrum, the vapour pressure attains a maximum in the forenoon. 



