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MR. A. W. RUCKER AND DR. T. E. THORPE ON A MAGNETIC 
Tables for the Calculation of the Magnetic Elements in the Future. 
We conclude this paper with Tables, by means of which the values of the magnetic 
elements may be determined during the next few years for any place in the United 
Kingdom. For this purpose we should know as accurately as possible—(1) the values 
of each element at the station at the epoch of the survey; (2) the secular change ; 
(3) the local disturbance. To determine the first of these, we give the next three 
Tables (VIII., IX., X.), in which the values of the elements deduced from the general 
formulae are given for all intersections within the kingdom of lines of latitude and 
longitude which correspond to whole degrees, together with the variation per degree 
of latitude and longitude. The method of using them requires no explanation. 
The values in the Table of Horizontal Forces display some irregularities. This is 
partly due to the fact, that a discontinuity is introduced along the line H = 17, on 
opposite sides of which we have used different formulae. The formula also, which is 
applied to the southern district, does not represent parallel lines, but lines of which 
the slope is a periodic function of the latitude. We have slightly smoothed the 
irregularities, a process which will introduce some discrepancies between the numhers 
given by the Table and by the formulae, but we have thought it better not to attempt 
to do away with all traces of the discontinuity. 
