80 



ON THE DIURNAL AND ANNUAL VARIATIONS OF 



An interpolating formula being constructed from the twelve monthly 

 means in the lowest line, on the assumption that they are the tempe- 

 ratures proper to the middle days of the several months; if the coeffi- 

 cients calculated on this erroneous assumption be multiplied respec- 

 tively by the following factors, the expression given below is obtained, 

 in which T„, denotes the daily mean temperature at any time w, 

 reckoned from January 15, the unit of time being the twelfth part of 

 the year. 



12 



12 



12 



Tn =42.82 -f 21.82 sin [n X 30 -f 256.48) + O.Y'Z sin (2ft X §0 -f 55) 

 + 0.18 sin (3?i X 30-}- 252) + 0.25 sin (4w X 30) 

 + 0.89 sin (5w X 30 + 5) + 0.14 sin (6?i X SO + 2*70) 



From the preceding equation which, by giving suitable values to 

 (»i), expresses the normal daily mean temperature at Halifax on every 

 day in the year, the mean temperatures of the warmest and coldest days 

 are found, together with the days of their occurrence, and the days on 

 which the daily mean passes through its mean annual value. 



Warmest day, August 28. Mean temperature, 64°. 90. 

 Coldest day, January 13, 14. Mean temperature, 21°.96. 



In Spring, the mean of the day is below the mean of the year on 

 April 29, and exceeds it on April 30. 



In Autumn, the mean of the day passes through its annual value 

 between October 25 and October 26. 



TABLE IV. 



