SURVEY OF THE BRITISH ISLES FOR THE EPOCH JANUARY 1, 1891. 279 
463a. Kew. See ‘^ 1890 Memoir,” pp. 16-0, 161, 162. 
The values of the elements used for Kew in the 1886 survey were those published 
for January, 1886. As we did not know the differences between our survey 
instruments and those in use at Greenwich and Stonyhurst, we treated all the 
observatories alike, and did not reduce them to the Survey Standard. 
The values for January, 1886, when reduced to January, 1891, by Table XTV., 
p. 531, are 
S=17°45'-0. H= 1-8193. d = 67° 31'‘1. 
The actual monthly means observed at Kew in January, 1891, were 
Sz=l7°45'-7. H = 1-8184. 6'= 67° 31'-8. 
As we now know, both from our own experience and from the observations of Dr. 
Rjjckevorsel, that the differences between Standard magnetic instruments are 
considerable, in the present paper we (1) reduce Kew to Survey Standard, (2) 
describe observations made with the Survey instruments at Stonyhurst, and (3) do 
not calculate the disturbing forces at Greenwich, the instruments at which have not 
yet been compared with those at Kew. 
Hence, the values finally adopted for January, 1891, as deduced from the epoch of 
the 1886 survey, are 
S=l7°42'-5. 1-8216. 6^=67°31'-1. 
4636. Kew. 
The means of the monthly means of the elements for December, 1890, and January, 
1891, at Kew are 
S=17°46'-2. H= 1-8175. ^ = 67° 3D-7. 
Reduced to Survey Standard, these become 
S=17°43'-7. H= 1-8198. d = 67° 3r-7. 
These are taken as the values for the epoch of the New Survey. 
