OF OBSERVATIONS FOR TEMPERATURE. 



25 



Rensselaer Harbor occurred in April, amount 9°.09, and in November, amount P.00 ; 

 showing a correspondence in amount but not in time. The diurnal variation never 

 disappears altogether, and even during the long arctic night there appears to be a 

 daily propagation or existence of a thermal wave producing a range of about 1°. 

 The amount of the amplitude changes tolerably regular from month to month ; 

 the high value in March, however, either presents a distinct feature or is due to 

 some anomaly. Altogether, the curve indicates no secondary maximum, such as 

 was found in September at Van Rensselaer Harbor. 



On the average, the maximum temperature is reached between noon and 1 P. M., 

 and the minimum between 2 and 3 A.M.; whereas, at Van Rensselaer Harbor, 

 these hours were respectively 2 P. M. and 1 A. M. 



The following table contains the hourly values of the diurnal variation for each 

 season and the whole year : — 



The computed diurnal variation for the whole year is derived from the expres- 

 sion given below. Comparing the means as stated above with corresponding values 

 derived in the preceding discussion of the mean temperature of the seasons, we 

 may add to each horizontal line the following corrections : to values for winter, 

 — 0°.05; for spring, +0°.30; for summer, +0°.29; for autumn, — 0°.78 ; for the 

 year, — 0°.0G. These differences arise from changes in the observing hours, and 

 consequent necessity of interpolation. 



The mean temperature of the day is reached at 7 h 2i m A. M. and at 6 h 56 m P. M. 

 by formula. The diurnal variation of the temperature during the whole year is 

 represented by the formula : — 



t = +2°.08 + 2°.02 sin (e + 252° 57') + 0°.25 sin (2s + 117.°) + n°.09 sin (3d + 251°). 



