Young, George, jr, Baxter, Hubert Eugene, joint author · New York, The Macmillan Co. · leaf 281
indicated above are frequently used in drawingcomplicated roof plans. , By this means it isoften possible to drawa complete roof planbefore any accurateelevations have beenmade.i 219. Lines of Level.From the considera-tions of § 218, it followsthat a plane may be fully described by a series of… … XIII, § 219] OTHER METHODS OF PROJECTION 265 These lines are called the lines of level of the surface. Theactual slope of such a plane, with respect to H, may be shownby passing a cutting plane, Z, perpendicular to the lines oflevel. This plane intersects X in the line a^f. Now let Z berotated into…
Geometry, Descriptive
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