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employment of Oblique Riders, 
although they are somewhat less calculated to add to the 
ultimate strength of the principal tie or shore, than if their 
direction had been longitudinal. To take, for example, the case 
of a ship’s arching or hogging : if the strength were overcome 
without any deficiency of stiffness, the upper decks and wales 
would be elongated, and the butts of the planks aloft parted, 
while the keel would be somewhat shortened', and the planks 
near it crippled, so that a ship 176 feet long and 40 feet deep, 
arching one foot with a uniform curvature, would have the 
length of the parts aloft, on the level of the quarter deck, 22 
inches greater than that of the keel. If, on the contrary, tlie 
strength were not overcome, but the stiffness only failed, the 
angular situation of the parts being altered, and the joints 
simply becoming loose without parting, the planks would slide 
on each other, and their square ends would no longer remain 
in the same vertical line at the ports, while there would be no 
material alteration in the comparative length of the decks and 
keel, nor any permanent parting of the butts of the planks. 
Grounds of decision respecting Oblique Riders, 
This comparison therefore brings the question, respecting 
tlie general utility of oblique riders, into a very narrow com- 
pass ; and we have only to inquire in what way it is most 
usual for ships to exhibit symptoms of weakness, in order to 
decide it. Now it will appear that, in cases of arching in 
general, some of the butts of the planks are always found to 
have parted aloft, at the same time that the angular position 
of some parts of the structure has as uniformly been more or 
less altered ; and very generally a certain degree of sliding is 
observable in the planks at the sides of some of the ports. 
