employmen t of Oblique Riders, 313 
any kind, the ship will naturally give way to the more per- 
manent pressure, which continues to act on her in the state of 
weakness thus superinduced. 
4. Breaking transversely. 
The pressure of the water against the sides of a ship has 
also a tendency to produce a curvature in a transverse direc- 
tion, which is greatly increased by the distribution of the 
weight, the parts near the sides being the heaviest, while the 
greatest vertical pressure of the water is in the neighbourhood 
of the keel. This pressure is often transmitted by the stan- 
chions to the beams, so that they are forced upwards in the 
middle: when they are unsupported, the beams are more ge- 
nerally depressed in the middle, by tlie weight of the load 
which they sustain ; while the inequality of the pressure of 
the water cooperates with other causes in promoting the sepa- 
ration of the sides of the ship from the beams of the upper 
decks. On the other hand, the weight of the mainmast often 
prevails partially over that of the sides ; so that the keel is 
forced rather downwards than upwards in the immediate 
neigliboLirhood of the midships. The tendency to a transverse 
curvature is observable, when a ship rests on her side, in the 
opening of the joints of the planks aloft, and in their becom- 
ing tighter below ; although this effect depends less imme- 
diately on the absolute extension and compression of the 
neighbouring parts, than on the alteration of the curvature of 
the timbers in consequence of the pressure. 
