Page:The Kinematics of Machinery.djvu/297

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64. The "Mechanical Powers" or "Simple Machines."

The mechanical arrangements which go by the name of " mechanical powers " or " simple machines " are familiar to all. Since the time of Galileo, or before it, they have been described in the majority of text-books as those arrangements to which, to a greater or less extent, all machines can be traced back, of which, in other words, they may all be regarded as compounded. As to the how and the whether, however, there has not been complete agreement; and it is specially noticeable, and at first sight astonishing, that the higher Mechanics _has more and more separated itself from any connection with these arrangements. For if they have really the meaning put upon them, and the contrary, in spite of the sceptics, is nowhere shown, they should here only acquire a higher value. The highest science could not then venture to overlook them, however homely or trifling they might appear to be, while in point of fact the notion seems to be gaining ground that while the "simple machines " are good enough for elementary mechanics, they are worthless for the higher part of the science.

If we look more closely into the question, and compare one text-book with another, we discover everywhere a doubtfulness as to the real significance of the ideas of which they yet retain the outward form. 46 Even as to the number of " mechanical powers" there is no unanimity. Some speak of six Lever, Inclined Plane, Wedge, Pulley, Wheel and Axle, Screw ; while others would include unconditionally the " funicular machine " * as a seventh. The definition of the " simple machine " fares even worse no two books can agree upon one. The most various places also are given to them in the treatment of the subject. Sometimes they stand at the beginning, sometimes in the middle, sometimes at the end, sometimes taken in different chapters; sometimes they are treated of without being called by their traditional names, as if with the suspicion that if they were acknowledged nothing

  • A cord suspended from both ends, and having weights attached to it at different

points. I have not noticed this among the mechanical powers in English works, but here generally the "toothed wheel" takes its place not to mention the "compound wheel and axle," &c., occasionally met with.

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