ON THE MAGNETIC DECLINATION. 



Value of a scale division 0'.453. 



One of the first questions to determine is how many of these residuals must be 

 used to give a definite result, and another one is whether numbers deduced from 

 different parts of the series would give harmonious results. To test both of these 

 the observations were formed into three groups — one containing 4,900 in 19 montlis 

 of 1840, '41 ; another, 6,715 results in 21 months of 1842, '43; and a third, 10,029 

 results in 1* months of 1844, '45. In all, 21,044 results. 



The following table contains the result for each group. Group II includes three 

 months of the hourly series of observations treated as if only equal in weight to 

 the bi-hourly series. 



The sign 2 indicates the algebraic sum of the values in the preceding tables for 

 the months comprised in each group, and for every hour-angle of the moon. The 

 lines headed I, II, III, contain the preceding values divided by their respective 

 number of months and expressed in minutes of arc, or the lunar diurnal variation. 



+ indicates west, — east, deflection from the normal position. 



