Young, George, jr, Baxter, Hubert Eugene, joint author · New York, The Macmillan Co. · leaf 198
t from the surface by any horizontal plane, is aninvolute of the circle (§ 134) which the plane cuts from thecylinder. These facts may be visualized without formal proof. VIII, § 169] CURVED SURFACES 181 159. To Draw the Projections of a Developable Helicoid ofTwo Nappes. Let the directing cylinder… … Fig. 173 the base circle, and extending to the involutes, as Vh^y, 2dx,etc. These lines are the H projections of elements of therequired surface (corresponding to fg in Fig. 172 (2)). TheV projections of 1, 2, 3, 4 are in HA, and those of w, x, y, zare in the plane of the upper base, HA. The…
Geometry, Descriptive
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