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Moriah, Tonypandy.-

A NEW INTERRUPTER.

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A NEW INTERRUPTER. In the Scientific American, Mr. Huck Gerns- back describes an interrupter for currents not exceeding four to six volts, on what he believes to be a new principle. This instrument when made according to the directions given will not consume more than i to 5 ampere, and will run as long as may be desired. A U-shaped baro- metric glass tube, about 15 centimetres in length, with a clear opening of about 3 millimetres, is heated in an oxy-hydrogen flame, and drawn out at the base of the U so as to leave a capillary bore not exceeding 5 millimetre in diameter. The tube is then partly filled with chemically pure mercury, and by drawing the air out of one limb of the U, the mercury is caused to pass through the capillary and to rise into the other limb, so as to stand at an equal height in each. The apparatus is placed in a vessel of water, and two thin platinum wires, connected with the battery, are passed into the mercury in either limb, so that a feeble current may be transmitted through the U tube. In the middle of the capil- liary there at once appears a bright bluish-green spark, accompanied by a sharply pitched note, indicating interruptions of high frequency. The explanation as giveii is that the instant the cur- rent is closed the mercury at the smallest cross- section of the capillary tube will become in- tensely heated and will begin to boil, and the force of the ebullition will cause momentary rupture in the column of quicksilver. This will be accompanied by a slight shock, and the ex- panding metal will rise in the limbs of the U. Of course a vacuum will be created at the point of rupture, and, as the tube is immersed in water, the mercury will cease boiling and will immediately become cool and contract. In consequence of the atmospheric pressure, com- bined with the weight of mercury in the limb of the U, the metal is almost instantly again brought into contact to be at once heated and driven apart as befojv n; cc.a, elor.i a.3 long as the current is maintained.

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Presentation to County\ Councillor…

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