80 
View of Mr Barlow’s Magnetical 
in a part of the world where the dip is very great, and where 
hitherto the compass has been considered as an useless instrument. 
Moreover, the attraction of this vessel, before leaving England, 
was very much greater than usual, so that on all accounts the 
nlate was in this instance submitted to the most severe trial. 
By a series of observations, made while the vessel was lying 
at the Nore, it was found that the bearing of a distant object 
differed 28°, with the ship’s head at east and west ; that is, the 
local attraction at each of these points was 14°, and proportion- 
ally great at all the other points,- — an excess of attraction which 
Captain Clavering attributed to the effect of the spindle of the 
patent capstan, a suggestion which was verified by experiment 
on the return of the vessel, as we have already stated. 
To counteract this strong power, it was necessary to bring the 
iron-plate, which was 14 inches in diameter, to a distance (from 
the middle of the pedestal) of 7§ inches; and the centre of it 7| 
inches below the pivot of the needle, in which situation abaft the 
compass , it counteracted the local attraction of the ship, and left 
the needle free to obey the natural directive power of the earth. 
This was proved by taking the variations of the needle with 
and without the plate, (as already explained in the Conway ex- 
periments,) from England to the North Cape ; when the close 
agreement of the former, and the great discrepancy in the latter, 
were so marked, that from this time the vessel was navigated 
during the remainder of the voyage altogether by the corrected 
compass, and with the best possible success. She was moreover 
swung in three different ports during the voyage, viz. at Ham- 
merfest, at Drontheim, and at Spitzbergen, and the local attrac- 
tion ascertained at every point ; first without and then with the 
plate : this was found to be at the east and west, or maximum 
points, without the plate, as follows, viz. 
Hammerfest, 
. 
• 
* 4 
4 
• 
24° 10' 
Spitzbergen, 
• 
• 
• • 
• 
4 
34 42 
Drontheim, 
• 
• 
• • 
•» 
• 
21 23 
England, 
• 
• 
• % 
% 
• 
14 00 
Whereas, with the plate affixed, the deviations were reduced to 
quantities very little exceeding what might be attributed to er- 
rors of observation. 
It will, however, be more satisfactory to state some of these 
results at length. 
