Appleton's cyclopædia of drawing, designed as a textbook for the mechanic, architect, engineer, and surveyor (1866)
Worthen, William Ezra, 1819-1897, [from old catalog] ed, Appleton, firm, publishers, New York. (1866. D. Appleton & co.) [from old catalog] · New York, D. Appleton and company · leaf 552
s upward is represented by white, and the intermediateslopes by diflerent j^roportions of black in the lines to white in the spacesintervening. We have not thought it necessary to give an illustration ofthis scale of shade, as it does not discriminate between slopes of greaterinclination than 45°,… … Fig. 20. Slope. \ Proportion ofBlack, j White. 2i^ or 2^3 1 10 5= or 63 2 9 lOO or 110 3 8 150 or 160 4 7 250 or 260 5 6 350 6 5 450 7 4 60O S 3 750 9 2 shade tabellated, the following are the proportions of black and white fordiflerent inclinations, and the construction may beeasily understood…
