A textbook on mechanical and electrical engineering (1902)
International Correspondence Schools · Scranton : International Textbook Co. · leaf 106
drawn in heavy lines. Exceptions to this rule are some-times made by experienced draftsmen, when a rigid adher-ence to it will produce a bad effect or will render thedrawing ambiguous. Fig. 72 shows a plan of a series of triangular wedges radi-ating from the common center O. The top is, of course,… … 45°, the direction of the arrows, would strike the side ofwhich 0^4 is the edge; hence, this side is a Hght surface,and tlie toi) being alsoa light surface, theline 0.1 must be light.OK, on the contrary, isa heavy line, since thelight cannot strike theside of which OK is theedge without…
