AT VAN 11ENSSELAER HARBOR. 



13 



Diurnal Range of the Declination. The diurnal range being an index to the 

 magnitude of the diurnal excursions, is best presented before the examination of 

 the diurnal inequality. The following table contains the highest and lowest scale 

 readings in the hourly series, and the maximum and minimum values observed, 

 together with the corresponding ranges. One division of scale = 0'.80. 



DAILY RANGE OF THE DECLINATION. 



The mean diurnal total range observed during the above period becomes 2 28'.6, 

 and the maximum diurnal range observed took place on the 14-15 February, and 

 amounted to 4 52'. 0. For comparison with similar quantities at other high lati- 

 tude stations we may take Lake Athabasca, where the greatest range in any one 

 day between October, 1843, and February, 1844, was 2 35', it happened October 

 16, 1843; at Fort Simpson the maximum range was 7 27', observed on the 16th 

 of April, 1844, in a series of observations extending over April and May, 1844. 

 The mean diurnal range during January and February, 1844, at Lake Athabasca, 

 was 31'. 4, and the mean range at Fort Simpson in April and May of that year was 

 1 12', these two quantities, however, were taken from the hourly series. 



If we classify the ranges according to this magnitude we obtain the following 

 results : 



Daily range less than 

 " " between 



1 



1 and 2 



2 and 3 



3 and 4 



4 and 5 

 " greater than 5 



1 

 6 

 4 

 3 

 3 

 



The diurnal range in the winter months, January, February, and March, when 

 compared with its annual fluctuation, is probably below the mean value of the 

 year. 



