First Principles of Mechanical And Engineering Drawing

difference, in character and application, which exists between it and that kind of drawing known as " freehand." The generic term " drawing," strictly speaking, is the art of representing objects on a surface?generally flat?by means of lines showing their forms and general contour, independent of colour or shading; for the latter, without form, would be meaningless and incapable of expressing anything. Freehand drawing is the practice of the art of drawing by means of the hand, the eye alone controlling and guiding the tool or instrument used for delineation. The hand guided by the eye can, however, only picture or draw what is seen from one position at a time ; for were it otherwise, a distorted view of the object would be the result, as its appearance to the eye from one point of view would be different to that from any other. All objects are made visible to the sense of seeing by the agency of light, whether natural or artificial, for without light it would be impossible to distinguish one object from another. To the artist or draughtsman, light is a stream of matter given off by a luminous body, travelling from its source in thin straight lines?or rays?to the object illumined, from which it is reflected or transmitted in the same way to his eye. What is seen, or is apparent to his sense of sight, he depicts or draws on his paper. If he changes his position with respect to the illumined object, he sees it differently, and obtains a different view of it; ...