A SUPER-SEARCHLIGHT.

Ashburton Guardian, Volume XLI, Issue 9430, 29 January 1921, Page 3

A SUPER-SEARCHLIGHT.

The production of art invisible searchlight, that can be used m sending messages for naval purposes without the possibility of detection, is the problem set, half m jest, half m earnest, by Admiral Bullard, of the United States Naval Communications Service. Mr W. D. Ryan, an authority on electrical illumination, promised that he would see what could be done to produce a cylindrical light core, rendered invisible by the use of infra-red rays. An incandescent lamp searchlight of .' 7,000^000 candle power was shown to some visitors, who evinced astonish- '' ment when Mr Ryan told them that : experiments had demonstrated that it was possible to increase a 600,000 candle-power light to 1,200,000 without additional electrical power, by simply conserVing lighivrays heretofore wasted. This waste was caused by the employment of parabolic lenses, he explained. The laboratory had discovered that searchlight lenses', if built with mirrors curved. on new lines 1 not parabolic, would conserve most of the lost rays, and the discovery was about to be put to the practical use of doubling the power of existing searchlights.