"TUMBLING JACK," THE NURSERY'S CONTRIBUTION TO THE PURSUIT.
In this example, and indeed throughout this article, we have not troubled about practical details of construction. These, of course, do not affect the principles involved. Much ingenuity indeed has been shown in their production, but the perpetual motionist cannot claim in them an exclusive property.
SHOWING HOW JACK WORKS.
The flopping-over arrangement just described reminds one of the "Tumbling Jack," a children's toy one often sees on sale in the streets. In this toy a series of bricks are strung together in a chain. From the ingenious way in which the bricks are joined it results, as everyone who ever seen it will at once remember, that on holding the uppermost brick in the hand and giving it an almost imperceptible tilting movement, an apparently endless series of bricks chase each other down the chain. Each brick in succession tumbles over and imparts an impulse to the one immediately below it, which in turn does the same, and so the motion is carried from one end of the chain to the other. Why could not this everlasting tumbling-down motion, which seemingly is produced without effort, be turned to account? It only needs the chains to be sufficiently multiplied in point of size or number to furnish us with a source of power which apparently may be made as large as we desire. Considerations of this kind wear a plausible air. But it may perhaps be noticed that when this particular apparatus is working, it is always held in the hand, and that our supposition about increasing the size or number of the chains would, as a consequence, carry with it the necessity for having either an army of persons, or a giant, to work the apparatus in its complete form. No magic need be invoked to explain the working powers of an army or of a giant.
THE GRINDSTONE PARADOX.
One has often heard of the miller who wished to drive his water-wheel by the water which the wheel pumped up to the "head-race," or supply conduit. Well, here is such an arrangement devised many centuries ago. On the left of the picture the water-wheel is shown receiving water raised by the "chain" pump on the right, suitable gearing transmitting the motion of the wheel to the pump.
THE MILLER'S DODGE FOR WORKING HIS MILL.