Page:Collected Physical Papers.djvu/32

12 the electric beam parallel, a pair of Analyser and Polariser, and a Receiver for detecting the electric radiation.

Electric oscillation is produced by sparking between two small platinum beads attached to hollow hemispheres and an interposed small platinum sphere (cƒ. fig. 1). The two electrodes are connected with the secondary ends of a modiﬁed Ruhmkorff coil. The usual vibrating interrupter was found to be a source of trouble, and was therefore rejected. A flash of radiation consisting of many electric oscillations is sufficient for a single experiment, and this was easily obtained by a sudden break of the primary current. To economise space, the coil was taken out of the supporting condenser box. Long strips of paraffined paper with tin-foil coatings were wound round the coil, and appropriate connections made with the interrupting key. The coil, about three inches in diameter and five inches in height, was placed vertically at one end of a small tinned-iron box, 6×4×7 inches. The metallic box screens the Receiver from electric and magnetic disturbances produced by the making or breaking of the primary current, the electric radiation being transmitted through a tube along the desired direction.

The box also contains a small storage cell and a tapping key, the press button projecting out of the box through a small hole. In front of the box there is a tube one inch in diameter and three inches long. To the inner end of this tube is fixed an ebonite square on which the radiator is mounted.

Polariser. Analyser and the Crystal-holder

At the further end of the tube is placed the Polariser,which may be a grating or any other form of Polariser,