distribution, &c. of the magnetic intensity in ships of war. 313 
was desirable to ascertain the intensities, being known, the 
same was determined at all the stations in the three differ- 
ent positions of the vessel ; first, when the principal section 
of the ship was in the plane of the magnetic meridian, and 
her head due north ; secondly, when the same section was at 
right angles to that plane, and her head due east ; and lastly, 
when the same section formed an angle of forty-five degrees 
with the magnetic meridian, and her head north-west.* The 
vessel was moored in the first situation, to discover the diver- 
sities existing in the magnetic intensity at the different sta- 
tions assumed ; and in the succeeding positions, to determine 
the changes produced in those intensities, from the imme- 
diate alteration which every individual force underwent 
from a change of position with respect to the primary mag- 
netic plane. 
The instrument employed for determing the intensity was 
similar to that denominated the apparatus of Coulomb ; con- 
sisting of a magnetized cylindrical bar, two inches and a half 
long, and g^ths of an inch in diameter ; delicately suspended 
by a single fibre of the silk-worm to the extremity of an 
adjusting screw, which worked in the cap of the glass ves- 
sel inclosing the bar. A brass wire likewise passed through 
the cap, having its lower end bent into an angular form, for 
the purpose of placing the bar in a direction at right angles 
to the magnetic meridian, previous to its being allowed to 
oscillate. 
On the different days devoted to the experiments, before 
visiting the ship, the time of making fifty vibrations of the 
* Captain Filmore, Commander of the ships in ordinary, at Plymouth, with 
the utmost readiness, moored the Scylla in the above positions. 
S S 
MDCCCXXIV. 
