MADE AT STONYHURST COLLEGE OBSERVATORY. 
75 
The Total Force. 
This can be at once deduced from the mean values contained in Tables I. 
For Epoch July 1st, 1866, IT. F. = 3-6028, and Dip=69° 45' 43" from April to Sept. 
For Epoch Jan. 1st, 1867, FI. F. = 3-6041, and Dip=69° 44' 59" from Oct. to March 
Applying the correction for the secular variation to reduce both these to a common 
epoch, we have for 
Jan. 1st, 1867, from April to September, T. F. = 3-6049 X sec. 69° 44' 48"=10-4136. 
October to March, T. F. = 3-6041 xsec. 69° 44' 59"=10-412S. 
which would make the intensity greater when the sun is further from the earth, the 
difference being very small, viz. 0-0008. 
This last result is opposed to that derived from the reductions of Sir Edward Sabine, 
but will have but little weight, both on account of the smallness of the amount, and still 
more from the uncertainty attached to the corrections applied for change of station. 
The above mean value of the total force, 10-4136, for January 1st, 1867, compared 
with the observations in October 1858, gives an average annual rate of increase = 0'0034, 
which agrees closely with the amount calculated by General Sabine (cf. Proceedings of 
the Koyal Society, February 1865). 
Whilst drawing up this paper I was not aware that Dr. Balfour Stewart was engaged 
in a similar reduction of a second six years’ series of the Kew observations, which has led 
to such a satisfactory confirmation of the results obtained by the discussion of the first 
six years’ observations at the same observatory. When another six years have elapsed, 
we shall be able to determine to what extent the results obtained above are due to local 
influences. 
