The following is an account of the work of M. Molteni on the projection value of various illuminants. The measurements were made with an ordinary lantern, the stage of which carried an opaque card in which was cut an aperture 0"7 centimetre square, while the distance of the lantern from the screen was such that each side of the square on the screen measured 1 metre. The screen was replaced by a disc of paper, the opposite side being illuminated by a standard lamp burning 42 grammes of oil per hour. The distance of the lamp was varied in order that equality of illumination might be obtained on the screen, and the photometric values of the light were determined from the distance of the lamp: - Multiple wick lamp, 1.00. Incandescent gas burner No. 2, no reflector, 1.00. Acetylene, with no reflector: No. 1 burner, 1/06; No. 2 burner, 1.10; No. 3 burner, 3.20; No. 4 burner, 4.10; No. 5 burner, 4.50. Limelight: alcohol and oxygen, 5.80; oxy-hydrogen, 16"60. Electric incandescent lamp, 32 candle-power, 0 68; 50 candle-power, vertical, 0.93; 50 candle-power, horizontal, 0.93; focus 100, 382. Arc lamps, 7 amperes: 39.03; 10 amperes, 75.61; 12 amperes, 86.50; 15 amperes, 117.61; 20 amperes, 160'80. The candle-powers of Welsbach incandescent burners are given on p. 297. It may be mentioned that a duplex oil-lamp will give a light of from twenty-eight to thirty candles.