Engraving and printing methods, advertisement illustration, technical- and trade-paper advertising, street-car advertising, outdoor advertising, house publications (1909)
Scranton : International Textbook Co. · leaf 293
Fig. 57 because this spot a> being half as strong, is twice the size ofspot by and therefore equal in value. In Fig. 59, the lightervalue a is balanced by the dark value b, although the latter
