6 ON DEDUCING THE MEAN TEMPERATURE OF A MONTH. 



method referred to, will exceed the average daily minirmim of the 

 month by exactly half the average daily range ; or, in other words, 

 by a quantity derived from the average daily range, by multiplying 

 it by the factor f or "5. Now the true mean temperature of a 

 month exceeds the average daily minimum by a quantity derived 

 from the average daily range, by multiplying it by a factor which 

 differs somewhat from "5, and has different values in different months 

 and in different localities. The values of these factors for each of 

 the twelve months have been calculated for Toronto, and are given 

 herewith. A table is also furnished, shewing for each month and for 

 all ranges, from 1° to 30°, the quantities to be added to the average 

 minimum temperatures of a month, in order to give the true mean 

 temperature of the month. 



The geographical limits within which these tables are applicable 

 cannot be stated with precision until similar investigations have been 

 entered into at one or more distant stations Probably, however, 

 they may be used throughout Upper Canada as far east as Brockville 

 and Ottawa, I regret that, owing to the manner of dividing the 

 day, adopted in the observations on which the calculation of the 

 tables was based, they can only be employed where the range is 

 reckoned as the difference between the highest and lowest tempera- 

 tures that occur during the period commencing and ending with 

 6 A.M. But as this mode is not convenient for observers in general, I 

 propose to carry on observations with a view of forming similar 

 tables adapted to a more convenient mode of reckoning the daily 

 range. 



TABLE T. 



Giving the factors by which the average daily range of the month mnst be 

 multiplied, in order to give the excess of the mean temperature of the 

 month over the average daily minimum temperature: — 



