For gas of a standard illuminating value, the lighting power increases with the temperature of the flame. It also increases, under favorable conditions, if the quantity of gas consumed by the burner in a certain period is augmented. Thus, two burners consuming 60 liters (rather more than 2 cubic feet) of gas, placed in juxtaposition, produce less light than one burner consuming 120 liters. As it is impossible to indefinitely increase the supply to ordinary burners, multiple-flame burners have been invented, in which two or more ordinary flames are united so that they may impinge upon each other. By an ingenious arrangement for bringing the air into contact with the multiple flames, two excellent types of lamps are obtained, consuming respectively 700 and 1,400 liters per hour, which meet with a rapid demand in Paris, and in many other towns, for lighting wide public thoroughfares, squares, and large open spaces. If, however, it is desired to obtain a flame with a much higher temperature, it is necessary to resort to a special arrangement for heating the air intended for combustion with the gas. The principle of heating the air by means of waste heat escaping with the products of the waste gas--the regenerative principle--was adopted by Mr. F. Siemens, and applied not only to gas burners, but to high temperature stoves. With the Siemens burner on the regenerative principle the following results are obtained: With a consumption of 150 liters per hour, the light of from 1 to 3 carcels; 250 to 300 liters, 6 to 7 carcels; 600 liters, 15 carcels; 800 liters, 20 to 22 carcels; 1,600 liters, 46 to 48 carcels; 2,200 liters, 72 carcels. Unfortunately, the construction of the Siemens Argand lamps is very delicate, and, moreover, they have the disadvantage of being heavy and rather unsightly. In Germany they have been widely adopted; but in France they have met with but little success. The Schulke lamp is made on the same principle; and this appears to be too delicate to come into general use. One of the latest burners of the regenerative class is the Wenham, which has been before the public for some time in England and is now being adopted in France. In point of fact it is merely a very effective improvement on Breittmayer's burner, from which it differs only in its construction; being produced in some elegant styles, which lend themselves perfectly to the decorations of private houses. The No. 2 lamp of this type, with a consumption of 283 liters (10 cubic feet) per hour, has given 126 candles, in a vertical direction without reflectors: horizontally, 50 candles. But the gas employed in the tests had an illuminating power about 20 per cent. higher than that usual in Paris. When experimenting in Paris with a No. 3 lamp in a vertical direction, it showed a consumption of 34.6 liters (1.2 cubic feet) per carcel obtained. The Wenham lamp is constructed to give light in a vertical direction; and by adopting a large reflector, the illuminating power