distribution , &c. of the magnetic intensity in ships of war. 321 
the stations 7" and S" ; and it is remarkable, notwithstanding 
it is generally supposed, that this part of the ship is less in- 
fluenced by iron than any other, — that the maximum inten- 
sity should have been found at the latter station, both in the 
first and third positions of the vessel : a proof, that sufficient 
care is not at all times displayed, in the employment of copper 
fastenings, &c., to a sufficient extent in the neighbourhood 
of the binnacle. A greater uniformity was also observed to 
prevail in the stations of the middle section, on the upper 
deck, when the ship’s head was east, than in the other posi- 
tions of the vessel. 
Notwithstanding the absence of the guns, shot, and other 
iron stores, from the vessel under consideration, the intensi- 
ties were found of a very diversified kind ; and in the pas- 
sage of the ship from one position to the other, the attractions 
were found to change in a very irregular manner from 
greater to less, and from less to greater. If therefore the 
different magnetic intensities, as determined in each position 
of the ship, be regarded as so many parallel forces, referred 
respectively to the three rectangular co-ordinate planes before 
assumed, it follows, that the position of the centre of force, 
corresponding to each system of intensities, may be readily 
determined for each co-ordinate plane, by means of the 
formula, 
r __ ij> + iy + iy + &c. 
x “ I+I'+I"+&c. ’ 
in which I, I', I", &c. denote the intensities at the respective 
stations; p,p',p", &c., the perpendicular distances of the 
corresponding stations, from the co-ordinate plane, to which 
the common centre of force is referred ;* and x the unknown 
• The letters «, (3, &c.. A, B, &c. a, b, & c. in the horizontal co-ordinate planes 
Tt 
MDCCCXXIV. 
