312 Mr. Harvey’s experimental inquiries relative to the 
part of the forecastle, and the after part of the lower deck, 
other planes were supposed to pass through the points A , a' ; 
M', m! , and C", d" , the two former being each 7 feet from 
the middle section, and the latter 6.5 feet. 
The before-mentioned planes having been assumed in 
situations, as remote as possible from the immediate influ- 
ence of the iron necessarily employed in the sides of the 
vessel, rhe masts, &c. ; stations denoted by the letters / 3 ", 7", 
l" , ike. B", C'. D", &c. ; h", d' , d", &c. , were selected in their 
several intersections with the decks, so as to be as free as 
possible from the irregularities of local attraction, and at the 
same time arranged in planes respectively parallel to the 
transverse co-ordinate plane. These parallel planes were sup- 
posed to meet the sections denoted by figures 1,2, and 3, Plate 
XVI, in the lines yyy'y", C C'C'C"', c dd'd" &c. ; intersect- 
ing the planes of the decks, denoted by figures 1, 2, and 3, 
Plate XV, in the lines d y C', d'y'C", d"<y'"C", &c. ; the longi- 
tudinal co-ordinate plane in P' P" V" , X' X" X"', &c. ; and the 
horizontal plane of the same name, in c y C, / % L, &c. Each 
point, therefore, where the intensity was to be determined, 
being at a given height above the deck, and in a vertical line 
produced by the intersection of a longitudinal and transverse 
plane, it’s position, with respect to the three co-ordinate 
planes, could be accurately ascertained ; and thence, if neces- 
sary, it’s actual situation in space.* 
The positions therefore of the different points, at which it 
* It affords me pleasure to bear testimony to the liberal assistance I received 
from Sir Byam Martin, and Sir Robert Seppings, by furnishing me with the 
drawings of the various ships I found it necessary to examine, during the prosecu* 
tion of these inquiries. 
