41816.) On the Stability of Vessels. ‘195 
following considerations, Suppose a wave, or any other power, to 
exert under the bottom of one of the scales a force equal to 2 ]b., 
it is evident that the momentum of the other, or descending scale, 
would-be 24;-but in the other case, and under the same~circum- 
stances, the momentum would amount to no more than 6,:because 
the length of the descending arm of the ballance was only 3 inches, 
or a fourth part of the length of the former case. This actually 
takes place’ toa certain extent when the head of a ship, after being 
lifted by a wave, falls into the hollow or trough of the sea; and the 
same reasoning applies to the rolling; consequently the motion 
round the longer axis of the vessel will be less when the guns are 
housed than when run out; and could the whole weight of the 
vessel be concentrated to a point, the oscillations would be the least 
possible ; but this mode of stowage would inevitably spoil the vessel, 
by causing it to bend downwards; therefore, to preserve the shape, 
the lading should be so disposed that the weight put on board each 
part of the bull exactly equal the weight of the displaced water. 
Much calculation might be saved, and very useful conclusions 
drawn, if actual models of ships were submitted to the same process 
as the models used in these experiments. It would be requisite to 
find the weight of the displaced water by calculation ; and this may 
be done sufficiently accurately from a draft, as I had a convincing 
proof, having spent many days in measuring and calculating the 
capacity of an 80 gun ship while on the stocks. I found the dis- 
placement of the water was 3343.2, tons of rain water, or 3434.1, 
tons of salt water, the specific gravity of rain water being to that of 
salt water as 1000 is to 1027. ..[ was favoured with the tonnage of 
the same ship calculated from the draft, and the difference was onl 
20 tons, which amounts to rather more than an inch in the ‘draft of 
water when the ship is loaded, it requiring 182, tons to bring down 
the vessel one inch in salt water. 
_ Example. 
Model 1. A parallelopipedon, Length, 24 inches. Breadth, 9 
inches. Total depth, 7 inches. Immersion, 41 inches. Weight 
of water displaced, 559-06 oz. 
