A Treatise On The Principles And Practice Of Harbour Engineering

CHANNEL DEMARCATION. 265 Tweiity-four of these candies unitedly gave a light équivalent to sixty-seven standard candles.1 In the later Eddystone of 1882, Douglass burners, with six conceutric wicks, attained an aggregate of nearly 80,000 candle-power. But the true standard of comparison is not so much the gross illumination as the intensity per unit of area. It is this intrinsic intensity which confers upon a beani its peuetrative power. The brightness of the flame section of the old wick burners ranged up to 70, or, at most, 80 candle-power per square inch, according to the number of the wicks. With incandescent mantles there is, generally speaking, an increase in intensity of 300 per cent., équiva- lent to about 200 to 250 candle-power, whileatthe same time the consumption of oil is reduced by nearly one-half. Fro. 232.—Matthew’s Burner. Frø. 231. —Pintsch Burner. Incandescent burners åre numerous, as well as varied, but they fall naturally into two main types or classes. One class is that in which vaporisa- 1 For a definite comparison of the varions illuminating agents, several units have been adopted or proposed. First, and most general in this country, is the standard candle burn- ing 120 grains of spermaceti per hour. In France the carcel lamp is the unit chiefly used. It burns 42 grammes of pure Colza oil per hour, and is equivalent to 9'8 English candles, 9'6 French candles, and 7 6 German candles.