Gases also expand. While water, and the different solids, all have their particular units of expansion, it is not so with gases, as all have the same coefficient
CHAPTER VIII[ToC]
HOW DRAUGHTING BECOMES A VALUABLE AID
The ability to read drawings is a necessary part of the boy's education. To know how to use the tools, is still more important. In conveying an idea about a piece of mechanism, a sketch is given. Now, the sketch may be readable in itself, requiring no explanation, or it may be of such a nature that it will necessitate some written description.
Lines in Drawing.—- In drawing, lines have a definite meaning. A plain circular line, like [Fig. 95], when drawn in that way, conveys three meanings: It may represent a rim, or a bent piece of wire; it may illustrate a disk; or, it may convey the idea of a ball.
Suppose we develop them to express the three forms accurately. [Fig. 96], by merely adding an[p. 96] interior line, shows that it is a rim. There can be no further doubt about that expression.