A Treatise on Mechanics

This Treatise on Mechanics, which was originally published in 1830, is the work of Dr. Lardner, with the exception of the twenty-first chapter, which was written by the late Captain Kater. The present edition has been revised and corrected by Dr. Lardner.

The quantity of space which a body occupies is sometimes called its magnitude. In colloquial phraseology, the word size is used to express this notion; but the most correct term, and that which we shall generally adopt is volume. Thus we say, the volume of the earth is so many cubic miles, the volume of this room is so many cubic feet. The external limits of the magnitude of a body are lines and surfaces, lines being the limits which separate the several surfaces of the same body. The linear limits of a body are also called edges. Thus the line which separates the top of a chest from one of its sides is called an edge.