The success of the optophone leads one to hope that it may be but the forerunner of a machine that will translate the whole world of light and color into one of music, and permit the blind not only to read by ear, but also to see their friends and their surroundings through the sense of hearing. In fact efforts to make such an apparatus preceded the invention of the optophone. THE WILLFUL GYROSCOPE As intimated above, we have included the gyroscope among the higher type of machines, because it seems possessed of a stubborn will of its own, and apparently defies the laws of gravity. There is nothing mysterious about its mechanism. It is merely a wheel with a heavy rim and with its axis mounted in gimbals, so that it may turn freely in any direction. The wheel, when at rest, behaves no differently from any other mechanism. But once the wheel is set to spinning at a high velocity it seems to acquire marvelous powers and obstinate notions of its own as to what it will do and what it won’t do. You may lift it, or lower it, or move it sideways in any direction, and it will not show the least sign of rebellion so long as the plane of its rotation is not deflected, but attempt to twist its plane of rotation and it will resist with the power of a giant. The resistance that even a small gyroscope will develop is astounding. A wheel weighing not more than 10 pounds may develop so much energy that a man twenty times as heavy pushing with all his might cannot turn it over. Not only does it resist the push, but it actually leans back against the pusher. Then it has the peculiar habit of turning at right angles to the direction in which it is pushed. Suppose, for instance, the axis of the gyroscope is horizontal and it is resting freely on a pair of supports, one at each end. Remove one of the supports and the gyroscope does not fall. To do so it would have to swing around the other point of support as a center; in other words, the plane of rotation would have to be turned angularly and such a motion the gyroscope resists. The unsupported end of the axis dips momentarily under the pull of gravity, but immediately recovers and actually rises above the horizontal, then it begins to revolve slowly in a horizontal circle about the supported end of the axis--a motion which is technically known as “precession”. The pull of gravity exerted in a downward direction results in a horizontal motion at right angles thereto. It seems as if the gyroscope was bidding defiance to laws that govern other objects, but, of course, such is not the case. The gyroscope is as submissively obedient to the laws of gravity as any other object or machine, but the forces which act upon it are so complicated that it is difficult for one to comprehend them without study. In fact, it is almost impossible to explain the strange behavior of a gyroscope without the use of mathematics that is too involved to be presented in this book.