FINE MEASUREMENTS

Evening Post, Volume CX, Issue 100, 24 October 1925, Page 7

FINE MEASUREMENTS

NEW WEIGHING DEVICE

USE FOB OIL PROSPECTING,

(UNITED TRESS ASSOCIATION— COVIKtQUT.)

(AUSTKALIAN-NISW ZEALAND CAULE ASSOCIATION.)

(Received 24th October, 9 a.m.)

NEW YORK, 23rd October

Believing that it will locate petroleum deposits better than the instruments now used, three oil companies have asked for duplicates of the most sensitive measuring instrument in existence, one which reacts to a weight of one 280-billionth part of an ounce. It was perfected by Professor Ralph 1-lart-sougli^, of the Physics Department of the Columbia University, which is financing an experiment to test the Einstein theory this winter. Believing Unit it will be possible' to multiply the sensitivity of tho instrument a thousandfold, the University 'will attempt -the weighing of molecules. Tho Hartsough instrument is now a hundred times as sensitive as the Eotvos balance. ° The latter is able to detect oil and metal doposils .by their weight, but is not fine enough to show how the sun and moon affect gravity at the earth's surface; Professor Hartsongh successfully recorded the effect produced in a fraction of a second by tho changing of position of the moon on tho gravitational attraction the earth exerts on an object weighing one twenty-nine thousandth part of an ounce. The apparatus utilises Michclson's interferometer, and tho measurements are made in wavelengths of light.

The Eotvos balance, hitherto the most sensiUvo gravity-operated instrument in use, is a metal tube balanced on a fine horizontal wire, the twistiii" of which as tho tubular beam moves out of the horizontal position serves to give a measure of the deileeting force. One end of the tube contains a small weight, and a similar weight is suspended from Hie other end by a long thread. The balance is exquisitely sensitive,, but dees not "weigh" iv the ordinary sense j it detects differences of gravitational force, and was developed by its originator for the purpose of studying gravitation. The measurement of very minute movements such as are caused by small forces or changes of force applied to comparatively rigid appnrtus has become easy since tho inteferometer was invented. This instrument introduces the wave-length of light as the unit, and enables moveincuts as small as a ten-thousand-mil-lioutli of an inch to be detected. Instruments which are very sensitive to gravity can be used in prospecting for oil because the resistance of large bodies of a light material below the surface is indicated by a slight reduction in the local fclce of gravity.