58 



REPORT — 1844. 



Sum of the pressures exerted by the force of the wind at Toronto on a sur- 

 face of one foot square at the several observation hours in IS^l, 184'2. 



Without ascribing anything Hke precision to the numbers in this table 

 (which are however likely to be more correct in relative than in absolute 

 value), they lead to the inference that the pressure of the wind, on the average 

 of the whole year, is doubled, or nearly so, between the coldest and warmest 

 hours of the day; i. e. between 6 a.m. and 2 p.m. The confirmation, or 

 otherwise, of this remarkable result by the observations of succeeding years 

 cannot fail to be a point of much interest. It appears from the registry of 

 Mr. Osier's anemometer, during four years at Birmingham, that at that sta- 

 tion the increase in the pressure of the wind is considerably more than double 

 between the hours of the minimum and maximum temperature. It will in- 

 fluence many reasonings if it shall be found as a fact of pretty general oc- 

 currence, that so large a portion of the daily wind is put in circulation to 

 supply an ascending current*. 



Synopsis of the Diurnal Variations at Toronto. 



* To the agency of this current we should probably ascribe the upward conveyance of the 

 vapour of increasing constituent temperature as the warmtli of tlie day increases, and which 

 appears to take j)lace more rapidly than the vapour might of itself make its way if the air were 

 tranquil. M. Kreil remarks (Mag. und Met. Beoh. Erster Jahrgang, p. 140), that in the sum- 

 mer months, when from the increased amount of the vapoiu- its effects are more noticeable, 

 the clearness of the sky decreases from the commencement of the morning to about noon, 

 and then increases uninterruptedly till towards midnight. And M. Dove notices (Met. 

 Untersuchungen, p. 53), that on fine calm days, when there is little lateral wind to disturb 

 the ascending current, the clear morning becomes clouded towards noon ; wliilst towards 

 evening, when the ascending cniTent has ceased, these condensed vapours, no longer up- 

 borne by its influence, descend into the wai-mer strata and are redissolved : hence the pecu- 

 liar transparency and beauty often observed in evening \-iews. 



