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Page:Popular Science Monthly Volume 89.djvu/96

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82

��Popular Science MontJih/

��Experimenting with the Siphon

ASlMPLY-constructcd siphon offers a most fertile field for amateur ex- perimentation. In some cases water can be made to How straight up twenty feet into the air until it passes the curve in

���Two tumblers, one higher than the other, joined by glass tub- ing, can be used to demon- strate the siphon principle

The water will easily flow to a height of six feet with the apparatus shown at the right

the siphon and Hows down again.

To carry on a series of ex- periments all the apparatus needed is a piece of glass- tubing and a connected piece of rubber-tubing. The glass tube may be bent in an alcohol flame, and a siphon so constructed that it will take water upward for six feet or more, and then downward in the other arm. If the joints are made tight the water will How even higher. VVhen the water has passed from one vessel into the other, the lower vessel may be raised, and back the water will flow, thus running uphill and down- hill. The only difficulty in this experi- ment, aside from making the joints light, is to fill the pipe at the start. This may be done by filling the entire pi|)e when the parts arc all on the same level. The ends may then be stoppetl and the one end raised into a perpcn- dii ular position.

Hill with all siphons of this kind the tr()ui)le is to establish a permanent con- duit between the two receptacles, since the siphon will exhaust itself unless the

���higher vessel is always kept filled. A siphon will not wait for a fresh supply of water, but will empty itself and cease to act.

Recently one experimenter was obliged to devise a means whereby the siphon would hold its contents and wait for a fresh supply. This was accom- plished by turning up one or both ends of the siphon. By this method a series of aquaria was connected so that water would run through the tubing and wait for a supply ; that is, a tiny stream would keep the supply to the siphon running continuously, and the siphon would hold the water running at a permanent height. Theoretically it is the push and not the pull that causes the water to run. The pressure of the air on the surface of the water in the upper vessel pushes the water up to take the place of what would be a vacuum. The action is simi- lar to the pull on the part of two pulleys, in which one is heavier than the other. It is evident that the hea\ier weight pulls up the lighter. So it is with the siphon. The curved angle of the siphon takes the place of the pulley, and the long arm full of water takes the place of the heavier weight. Once the long arm full of water starts it "pulls" the contents of the shorter arm.

���How the glass tubing is arranged when two largo jars of water arc to be siphoned. The test may be carried on indefinitely by reversing the position of the tubes

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