OF VESSELS, OCCASIONED BY LOCAL ATTRACTION. 
217 
These rules, which are given upon the supposition that the compass is situated 
in its usual place, aft in the vessel, will furnish a general idea of the direction 
of the deflection. With regard to the actual amount, it is of course different 
in different vessels, varying in these latitudes from 5° to 12° or 1 4° with an 
easterly or westerly course ; which become greater as we increase our latitude, 
but diminish (without however vanishing) at the equator, whence it again 
increases as we approach the southern pole. 
The following are some results, several of which I have assisted in taking ; 
they rest, as will be seen, on the best authorities, and will give a good general 
idea of the maximum amount. 
Ship. 
Commander. 
Place. 
Local Attraction. 
Conway . . 
Captain Basil Hall . 
. Portsmouth . 
o 
4 
32 
Leven . . 
Captain Owen . . . 
. Northfleet 
6 
7 
Baracouter . 
Captain Cutfield . . 
. Northfleet 
. 14 
30 
Hecla . . 
Captain Sir E. Parry 
. Northfleet . 
• 7 
27 
Fury . . . 
Captain Hopner . . 
. Northfleet . 
6 
22 
Griper . . 
Captain Clave ring . 
. Nore . . . 
. 13 
36 
Adventure . 
Captain King . . . 
. Plymouth 
7 
48 
Gloucester . 
Captain Stuart . . 
. Channel . . 
9 
30 
Giving a mean of 8° 44' at the east and west points in these latitudes. 
The latter observation by Captain Stuart is from the remark-book of the 
Gloucester, and from which I beg to give the following extract : 
“ 1830. 30th August. From not having had a favourable opportunity of 
ascertaining the ship’s magnetism or local attraction in steering down the 
British Channel, I only allowed the true variation as found, but observed the 
ship was invariably drawn to the southward of her intended place, notwith- 
standing the greatest care being taken in steering her. But on taking an am- 
plitude of the sun at setting on the 1st September, I found the variation to be 
34° W. (when the ship’s head was west), which difference from the true varia- 
tion in the Channel 24° 30' W. will account for the ship being so drawn to the 
southward of her intended track.” 
It would be quite superfluous to give further evidence of the existence of 
2 F 
MDCCCXXXI. 
