ON BEDUCING THE MEAN TEMPERATURE OF A MONTH. 5 



In Chateau Riclier below Quebec, a band of limestone occurs about 

 a mile from the fossiliferous deposits, and to the north-west of it lime- 

 feldspars present a breadth of eight miles. On an island near 

 Parry's Sound on Lake Huron, Dr. Bigsby observed the occurrence in 

 situ of the opalescent variety of labrndorite, and the name of the min- 

 eral reminds us of the existence of the rock beyond the eastern end 

 of the Province. It thus appears probable that a range of rock will 

 be found winding irregularly from one end of the Province to the 

 other, of sufficient importance to authorise its representation by a 

 distinct color on the map, and a distinct designation in geological 

 nomenclature. 



ON DEDUCING THE MEAN TEMPERATURE OF A MONTH. 



BY G. T. KINGSTON, M. A. 



PEOFESSOE OF METEOEOLOGT, UNIVEESITT COLLEGE, TOEONTO. 



Bead before the Canadian Institute, December 12th, 1857. 



The mean temperature of a day is commonly derived from the 

 temperatures observed at three or more stated hours, by applying to 

 their arithmetic mean a certain correction, the amount of which 

 experiment has revealed : but as this method demands the personal 

 attendance of the observer, at the stated hours— an inconvenience 

 to which many people are unwilling to submit — it is very desirable 

 that the maximum and minimum self-registering thermometers be 

 made available for the same end. 



It was the practice formerly to consider the arithmetic mean be- 

 tween the highest and lowest temperatures of a day as its mean 

 temperature— an estimation in which no regard was paid to the 

 time that the several component temperatures continued. This was 

 obviously a very serious omission ; for if the mean temperature of 

 a day be regarded as an index of the total effect produced by heat 

 during that day, the duration of the separate component tempera- 

 tures ought certainly not to be left out of consideration. 



The mean temperature of a month, when the mean temperatures 

 of the several days that compose it are obtained by the inaccurate 



