Dr. Percy Frankland has obtained results which may be thus briefly summarized: (1.) That pure ethylene, when burnt at the rate of 5 cubic feet per hour from a Referee's Argand burner, emits a light of 68.5 standard candles. (2.) That the illuminating power of equal volumes of mixtures of ethylene with either hydrogen carbonic oxide or marsh-gas is less than that of pure ethylene. (3.) That when the proportion of ethylene in such mixtures is above 63 per cent. the illuminating power of the mixture is but slightly affected by the nature of the diluent. When, on the other hand, the proportion of ethylene in such mixtures is low, the illuminating power of the mixture is considerably the highest when marsh-gas is the diluent, and the lowest when the ethylene is mixed with carbonic oxide. (4.) That if 5 cubic feet of ethylene be uniformly consumed irrespectively of the composition of the mixture, the calculated illuminating power is in every case equal to or actually greater than that of pure ethylene until a certain degree of dilution is attained.

This intrinsic luminosity of ethylene remains almost constant when the latter is diluted with carbonic oxide, until the ethylene forms only 40 per cent. of the mixture, after which it rapidly diminishes to zero when the ethylene forms only 20 per cent. of the mixture. When the ethylene is diluted with hydrogen, its intrinsic luminosity rises to 81 candles when the ethylene constitutes 30 per cent. of the mixture, after which it rapidly falls to zero when the ethylene amounts to only 10 per cent. In the case of mixtures of ethylene and marsh-gas, the intrinsic luminosity of the former is augmented with increasing rapidity as the proportion of marsh gas rises, the intrinsic luminosity of ethylene, in a mixture containing 10 per cent. of the latter, being between 170 and 180 candles.