employment of Oblique Riders. 331 
curvature proportionally greater from the other strains, which 
have been already calculated. Mr. Seppings has also very 
properly introduced, in the Tremendous, an additional kelson 
on each side of the step of the mainmast, in order to support 
its weight, and to prevent the partial sagging of the keel. 
1 
10. Riders. 
With respect to the transverse strain, or the tendency of 
the sides to sink in comparison with the keel, some strength 
is probably gained by Mr. Seppings's mode of fixing the filling 
timbers in the same manner as the frames: and some advan- 
tage must be attributed to the cooperation of the wedges, or 
fillings in, with the timbers, as far as their connexion is capable 
of bringing them into action. The common cieling is by no 
means advantageously placed for assisting in a resistance of 
this kind, since it can only act where the curvature would be 
increased by the bending of the sides, and even there can only 
be compressed in a transverse direction (fig. 7). The riders 
be reduced in the ratio of i to i— .98'’' r: .0786. Now when a cylinder is im- 
mersed to the depth of its axis, the calculation of the effect of the longitudinal pres- 
sure exactly resembles that of the stiffness, the strain being to that which would be the 
effect of the pressure on the ends of the circumscribing prism as | x •7854 = -58505 
to I : but the strain on the prism would be :z: 50 x 25 x 12.5 X — : 35 =7440.5, 
and for the cylinder, af — 4383 and since the height of the modulus of elasticity of 
oak. is 5060000 feet, (p. 509), and its specific gravity nearly equal to that of water, 
or perhaps a little greater, we have m = 5060000 X 50 x 50 x -7854 ; 35 tons, 
, , ^ 50^ X 5060000 X .7854*- ^5 
and the radius of curvature .0786 -r-T' =-0786. -7 5 7 : — 7 
/ i 6 aj 16 X i X .7854 X 50-^; (24x35) 
5060000 
r: .0786 . = 795432 feet; and dividing the square of 90 by twice this 
number, we have .005 1, or one sixteenth of an inch, for the versed sine or arching. 
