336 Mr. Harvey’s experimental inquiries relative to the 
longitudinal sections alluded to, in fig. 3, Plate XVII., and are 
introduced into the diagram, to exhibit the relative situations 
of the stations on the lower deck, with respect to the ballast 
and tanks. 
On the after part of the upper deck, as shown in fig. 1 , Plate 
XVII., the stations in the starboard and larboard sections, 
were less numerous than in the middle section, on account 
of the difficulty of finding points, as far removed as possible 
from the influence of the carronades, and which in this part 
of the ship were at right angles to its sides. In the after 
part of the middle deck, or in the Captain’s cabins, the sta- 
tions were more numerous ; fifteen having been selected for 
the purpose of particularly discovering what varieties of in- 
tensity existed in this part of the ship, in order to form an 
estimate how far the magnetic changes were likely to affect 
a chronometer when placed in the cabin. With the same 
view the stations in the after part of the lower deck, fig. 3, 
Plate XVII., were assumed; because in this part of the 
vessel are the births of the lieutenants and master, and in 
which chronometers are sometimes deposited. 
In the middle section, on the upper deck, it was found that 
the intensity attained its maximum at tf, at the distance of 
4 feet 5 inches before /, the position of the binnacle. After 
passing the point of greatest intensity, a sudden declension 
of its power was observed at /, and which was farther con- 
tinued to f # , where it became a minimum, after which it re- 
ceived an augmentation at d. At s, the station between the 
binnacle compasses, a great uniformity was observed in the 
results of the oscillations ; and it was farther remarked, that 
the intensity at the station, e', was an exact mean between 
