HOURLY CORRECTIONS FOR PERIODIC VARIATIONS, 



OR 



CORRECTIONS TO BE APPLIED TO THE MEANS OF THE HOURS OF OBSERVATION, OR 



SETS OF HOURS, IN ORDER TO OBTAIN THE TRUE MEAN TEMPERATURES 



OF THE RESPECTIVE DAYS, MONTHS, AND OF THE YEAR. 



THE following set contains all the tables for correcting the means of observations 

 on atmospheric temperature for the effect of diurnal variation which have been pub- 

 lished by Dove, together with a few others of the same description. Dove's tables 

 are found in two papers, published in the Memoirs of the Royal Academy of Berlin 

 for 1846 and for 1856, and in the first Report on the Observations of the Meteoro- 

 logical Institute of Prussia, Berlin, 1851. 



In the first paper are twenty-nine tables, in Reaumur's scale, nine of which have 

 been republished, in Fahrenheit's scale, in the Proceedings of the British Associa- 

 tion for 1847, and will also be found below. In that series the corrections have 

 been formed by finding first the differences between the hourly and the true means, 

 and then computing the observations by Bessel's formula, in order to eliminate the 

 accidental irregularities due to the shortness of the period during which the observa- 

 tions were taken. Calling x the horary angle reckoned from noon, Bessel's for- 

 mula is 



tx = u + u' sin (x -f- U>) -f u" sin (2 x -f U") + u 1 " sin (3 a; + U 1 "). 



