distributions , &c. of the magnetic intensity in ships of war. 335 
the side course of iron tanks in rt' <r v <p'. These planes pro- 
duced the sections, fig. 2 and 3, Plate XVIII. ; the stations 
E e'" , F ,f’" being orthographically projected on them. 
The station % in the middle section was assumed midway 
between the binnacle compasses. In this section, no stations 
could be obtained on the upper deck between the points 
t and I', on account of the stowage of the boats, the ships 
gear, &c. ; nor could any station be assumed on the middle 
deck farther forward than x" , on account of the pens for the 
sheep, fowls, &c., and the galley. The station &" was taken 
in the lower deck, so as to be nearly over the middle of the 
mass of ballast ; and the station x'", just above the after bulk- 
head of the shot locker. The point a'" was also assumed 
over the hatchway of the iron tanks ; and the station a'"', 
immediately below' the former point, and about two feet 
above the surface. The station v" was taken as nearly as 
possible to the foremost extremity of the tanks. 
The diagram denoted by fig. 1, Plate XIX., is a horizontal 
section of the ship, passing through the upper surface of the 
middle tier of tanks. The tanks are denoted by the letters 
< rtuvii / 1 \ and the ballast by srqq' r' s' ; the iron pigs com- 
posing the mass being represented by the small rectangular 
parallelograms. The single dot in the middle of some of the 
rectangular spaces, implies, that the ballast in that part is 
one pig deep ; two dots, two pigs deep ; three dots, three 
deep, and so on. The rectangular space vwv'w ', is a hori- 
zontal section of the well which contains the main mast, 
chain pumps, &c. ; and the parallelogram w x w' x', that of 
the shot locker. The dotted lines passing through E"V", 
F '"f", and N'" ri", may be regarded as continuations of the 
