28 6 Mr. Atwood's Disquisition on 
partly on the construction and equipment of the vessel, and 
partly upon the distribution of the lading and ballast, which 
circumstances therefore determine the distance GE, or the dis- 
tance between the centre of gravity of the vessel, and that of the 
displaced volume. 
These several conditions having been determined, the con- 
struction of the vessel's stability will be as in the former cases. 
Through the point E, draw the line EV parallel and equal to 
the line PQ ; and, in EV, take ET to EV as the volume im- 
mersed by the inclination is to the entire volume displaced ; or 
as A to V. Through the centre of gravity G, draw GU parallel 
to CH, and through the point T draw TZ perpendicular to GU. 
GZ is the measure of the vessel's stability, when inclined from 
the upright through the angle ASH. 
The weight of the vessel and lading is found from the fol- 
lowing proportion:* as i cubic foot is to V, the volume dis- 
placed, so is ~ part of a ton to the vessel's weight, which will 
therefore be — — ton. 
35 
The arithmetical operations required for ascertaining the sta- 
* According to Mr. Cotes, (Hydrostatics, page 73,) the specific gravity of sea 
water is — 1.03, when that of fresh water is — 1 . And, since the weight of a cubic foot 
of rain water is 1000 oz. or 6z£ pounds avoirdupois, it will follow, that the weight of 
a cubic foot of sea water is 62.5 x 1.03 = 64.375 pounds avoirdupois. Mr. Chapman, 
in his Treatise on the Method of finding the proper Area of the Sails for Ships of the 
Line, infers the weight of an English cubic foot of sea water to be 63.69 pounds avoir- 
dupois. If an average between these results be taken, the weight of a cubic foot of 
sea water will be very nearly 64 pounds avoirdupois ; and the weight of 35 cubic feet 
of sea water will be almost exactly one ton. According to the tables published by M. 
Brisson, the specific gravity of sea water is 1.0263, when that of rain water is 1. By 
computing from this specific gravity, the weight of a cubic foot of sea water will be 
64.14 pounds avoirdupois. 64 pounds avoirdupois is assumed as the average weight, 
in the ensuing computations. 
