“After a trial of a multitude of implements and machines, we fall back on those of the most simple form, other things being equal. The crow-bar has been employed from time immemorial, and it will not likely go out of use in our day. For simplicity nothing exceeds it. Spades, hoes, forks are of similar character. The plow, though made up of parts, becomes a single thing when all are bolted and screwed together. For this reason, with its moderate weight, it moves through the soil with little difficulty--turning aside for obstructions, on account of its wedge form, when it cannot remove them. The harrow, although composed of many pieces, becomes a fixed, solid frame, moving on through the soil as a single piece. So with simpler cultivators. Contrast these with Pratt’s ditching machine considerably used some years ago, but ending in failure. It was ingeniously constructed and well made, and when new and every part uninjured, worked admirably in some soils. But it was made up of many parts and weighed nearly half a ton. These two facts fixed its doom. A complex machine of this weight moving three to five feet per second, could not strike a large stone without a formidable jar, and continued repetitions of such blows bent and deranged the working parts. After using a while, these bent portions retarded its working; it must be frequently stopped, the horses becoming badly fatigued, and all the machines were finally thrown aside. This is a single example of what must always occur with the use of heavy complex machinery working in the soil. Mowing and reaping machines may seem to be exceptions. But they do not work in the soil, or among stones; but operate on the soft, slightly resisting stems of plants. Every farmer knows what becomes of them when they are repeatedly driven against obstructions by careless teamsters.” Simplification Has Limits. In discussing form we saw that simple shapes, such as those of sticks cut from a cylindrical tree, are not so strong as the less simple forms of hollow cylinders. We found that a joist, of plain rectangular section, is not so good a burdenbearer as a girder whose section resembles the letter I. If a slide for a timber is to be built on a mountain side, a novice would suppose that a straight inclined plane would afford the speediest path for the descending wood. Not so. More speedy is a slide contoured as a cycloid, the curve traced by a pencil fastened to the rim of a wheel as the wheel rolls along a floor beside a wall against which the pencil presses. Not all tasks are simple, so that it is often best to build and use a machine as complicated as a turret-lathe or a Jacquard loom. Whatever the inventor seeks first, last and all the time is Economy; to that end he adopts whatever means will serve him best, whether simple or not. Professor A. B. W. Kennedy, famous as a teacher of machine design, says:--