MAGICAL SCALES.

Pelorus Guardian and Miners' Advocate., Volume 22, Issue 45, 13 June 1911, Page 2

MAGICAL SCALES.

WEIGHING A SEVEN-THOUSAND

MILLIONTH OF AN ODNOB.

To .a small underground chamber below his own laboratory at University College, London, Sir William Ramsay, the famous scientist, recently led a visitor. “I will show you,” he said, "a pair of scales which will weigh a seven - thousand - millionth of an ounce.” The room was in semi-darkness. So delicate are these wonderful scales that their balance is disturbed by' the alteration of temperature caused by the turning on of an electric light at the other end of the room. The operator has to leave them for an hour in darkness —after he has tip-toed from the room so that hu footfall should not set up any vibra tion—and then read them swiftly be fore any change in the temperature has bad time to affect them. The scales rest in a metal chamber. The beam, only a few inches long; appears a mere cobweb of glass witb its frail supports. It is not made of glass, however, explains Sir William, but of silica, which expands and contracts under the effect of heat far less than glass. Hanging from one end of the beam of the scales by a strand of silica fibre so slender that it is scarcely possible to see It is a stay. Upon this is placed a minute glass tube. Imprisoned in the tube is a whiff of Xenon, a gas discovered by Sir-Wil-liam Ramsay. The movement of the scales when the tube is dropped inpoO | them is so slight that it cannot •be j detected at all by the eye. But the I movement ife made to swing froni side to side a tiny mirror, Upon which a beam of light 1s focused. The result is that a shifting point of light is thrown upon a graduated black scale six feet away. The weight of the tube, with the gas it it, is then recorded by the movemenl of this pin-point 0 ! light on the scale. Then comes the interesting teat The ,gas is released from the tube, which is weighed again. It is flow found to weigh a two-hundred-and-fifty-thousandth Of a milligramme, or a seven-thousafid-miilibnth Of an ounce, less, than it did when idle, gas was in it. Therefore the .weight Of this whiff of gaS whs d Seven-thou-sand-millionth of &n Ounce. *Thc smallest Object that can be picked up with the most delicate forceps is a piece of alumidiunl wifi far thinner than A human hair, a 25th of an inch jri length; which Weighs a fourteen-hundred-tfaousandth Of hn ounce. It edri scarcely be Seed, and it is difficult td detect whether it is resting on the scales Or hot. A section of aluminium wife Weighing ar eighty-four-huhdred-thousandth Of, hn ounce can bd prepared. But it is only visible in a microscope. For this reason weights of less than a fourtcen-hundred-thousandth Of An ounce have to bd registered in gaSes. —‘‘Tit-Bits.v