SPYING UNDER EARTH

Greymouth Evening Star, 9 April 1927, Page 8

SPYING UNDER EARTH

WIRELESS OUTFIT DESCRIBED.

The history of mining is full of yarns about the tricks for passing off dud mines on the innocent and even successfully on the wise; of the million and one ways for salting a mind. These days will soon be past history, for closb on the heels of television we are being given some hints of the methods of seeing what is under the earth. No need for boring to take samples of the actual ore and no blind boring where ore is not, if all that is claimed of this new use of wireless currents be true.

It is calculated that the cost of boring for oil in America has cost millions. In the Rand boring operations to find where the deeper gold-bearing strata lay must too have run into very large sums of money. Such expensive preliminaries will be eliminated. Listening to the earth is now iu fact possible equally with the hitherto gnKeard of feat of listening to your face.

Hints of how to spy out, not the land, but what is below it, were obtained during the war. It is believed that an Austrian engineer, engaged in listening-in to enemy conversations by using wireless earth, telephones, made observations on the conductivity of various rocks and minerals. It was from these war-time notes that the development of electrical prospecting received its impetus. Germany has made use of this knowledge and carried it on farthest, but other countries are exploiting it, notably France and Sweden, and research into it is now world-wide. An English engineer in Rhodesia.who has worked on these lines recently located copper. For the sake of the expert we quote a description of the German outfit. This comprises a portable dynamo, generating an alternating current, iron rods about 18in. long, driven into the earth at distances of one mile apart, which serve as electrodes, together forming the transmitting apparatus. Reception is provided for by an enclosed frame aerial mounted on a stand connected up with an amplifier, and the aerial can be moved about or both a vertical and a horizontal axis A current, which is pecked up on the aerial from the electro-magnetic lines of force passing thorugh the earth is amplified several thousand times be-

’ore it reaches a telephone receiver. By noting the direction and the inclination at which the aerial must be turned in order always that a minimum intensity of sound from this current will be heard in the telephone, it is possible to draw graphs, from which the exact position and depth of any mineral deposit, of water, oil or rock strata, can be shown. Since these processes are dependent on differencs of lectrical conductivity, they do not indicate the actual composition of any deposit, but do show whether the deposit is one of good conductivity like copper ore, or of bad conductivity like oil.