PIERHEADS, QUAYS, AND LANDING-STAGES.
213
When D=C
2
the hyperbolic portion vanishes and we get the special case
of a pontoon immersed to one-half its depth, the investigation of which occupied
our attention at the outset.
Method of tracing' parabolic and hyperbolic curves.—Para&o/a.
Fig. 187. —Parabola.
Fig. 186.—Hyperbola.
Divide the semi-base and the height into an equal number of parts, as shown
in fig. 187. Draw lines parallel to the axis through each of the points on
the base, and join the points on the sides to the vertex. The intersections
give points on the curve.
Hyperbola (see fig. 186). —The curve required is the rectangular hyper-
bola, and the distance a from the centre H to the vertex B is given. Draw
the axis HX bisecting the angle GHK. With centre H and radius a,