After a brief review of the development of high-pressure mercuryvapour lamps and their applications, the present position is considered, both as regards the understanding of the properties of the discharge itself and the applications to lighting. Some attempt is made to examine the ultimate possibilities of the discharge from the point of view of efficiency and colour. Present applications are discussed, and the demand that future applications are likely to make on lamp design are considered. 00) = /* : == P I V %•a •-P

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