Electric lighthouse lamps, 1949.
© Science Museum / Science & Society Picture Library
On the left is shown a 10,000 watt lamp, whose filament differs greatly in shape from the oil or gas flames utilised in earlier lighthouse lamps. The expensive optics used in a lighthouse would have required significant redesign if a conversion to such an electric bulb was to be made. The 5,000 watt lamp on the right, however, which includes a Stanocil diffusing cylinder, overcame these disadvantages by surrounding the filament with a translucent cylinder of silica. A domestic 60 watt lamp is shown for comparison.