Appleton's cyclopaedia of drawing : designed as a text-book for the mechanic, architect, engineer, and surveyor : comprising geometrical projection, mechanical, architectural, and topographical drawing, perspective and isometry (1869)
Worthen, W. E. (William Ezra), 1819-1897 · New York : D. Appleton and Company · leaf 354
5, 56, 57. Fig. 55. Fig. 56. Fig. 57. In these figures, lines *======= represent parts required to resist compression ; lines parts to resist tension only ; lines — - parts to resist both tension and compression. In a triangle (fig. 55), an angle cannot increase or diminish, without the opposite… … completely braced, as each does not permit of an effect taking place, which would necessarily result from a change of figure. Hence also, any system
