employment of Oblique Riders, 315 
tocks, whicli are their immediate continuations, being broken 
off; and sometimes the opposite ends of the floor timbers are 
forced out, especially in large ships without riders, their at- 
tachment to the keel remaining unimpaired. 
7 . Decay, 
The causes which promote the decay of timber are only so 
far understood, as we are acquainted by experience with their 
effects. A partial exposure to moisture appears to be by far 
the most 2;eneral of these causes : it is well knowm that total 
submersion does not accelerate decay; a surface wdiich is kept 
moist by imperfect contact with another, so that a portion of 
water is retained between them by capillary attraction, seems 
ahvays to be the part at wiiich the timbers begin to rot; while 
both the surfaces completely exposed either to the drier air, or 
to the water, and those which are wedged closely together, 
and press strongly against each other, remain perfectly sound. 
8 . Means of resistance. 
We are next to inquire into the comparative advantages of 
different angular positions of the timbers of a ship for resisting 
the forces wiiich have been described ; and in particular how 
far the arrangements, which have been proposed by Mr. Sep- 
PINGS, are better calculated for the purpose, than the common 
modes of construction. Wliatcvcr opinion we may ultimately 
form of these arrangements, they are by no means sufficiently 
justified by the experiments which have been exhibited in 
illustration of them. These experiments show, that when 
tw'o parallel planks, (Plate XL, fig. 1,) have loose pieces in- 
terposed, extending perpendicularly from one to the other. 
