Page:The American Cyclopædia (1879) Volume X.djvu/137

 LAMP LAMPBLACK 131 FIG. 1. Davy's Safety Lamp. mines, contrived a lamp which was protected by a glass cylinder, and covered at top with a perforated metallic cap to allow the products of combustion to pass out. The air to support combustion was admitted through small open- ings in the bottom, and it was supposed that the velocity of the current en- tering the lamp would prevent the explosion passing backward ; but the protection the lamp af- forded was really owing to the smalmess of -the apertures, con- tinued through capillary tubes till they discharged all around and close against the circular burner. Davy's lamp is represented in fig. 1. The wire-gauze cylinder, through which the air was ad- mitted, served also for the pas- sage of the light, and when com- posed of wire -fa to -fa of an inch in diameter, and with 28 wires or 784 apertures to the inch, proved a perfect obstruction to the flame in the most explosive mixtures, unless these were blown in currents through the gauze, or the lamp was carried rapidly through the gas. The wires might even be heated red hot, as sometimes happens in very foul air, by the flame leaving the wick and burning in the upper part of the cylinder, and no explosion take place; but if a glass cover became hot it might be broken by drops of water falling upon it ; and so fragile a ma- terial under any circumstances could not be regarded as a sure protection. Among the va- rious modifications of the Davy lamp, that known as Mackworth's safety lamp, which was contrived by one of the government inspectors of coal mines to meet the objections raised in resisting the general in- troduction of the Davy lamp into the fire-damp mines, is represented in fig. 2. The objections were the small light giv- en by the Davy, which is an inconvenience in working high seams of coal ; that its locks could be easily picked and opened by the work- men to obtain more light, or to light their pipes ; and also the dan- ger of breaking the glass already mentioned. The lamp has a thick outer glass, a a, and a thin inner chimney, fb. The air supplies the flame in the direction of the arrows through three wire gauzes : first the cylindrical gauze c ; then through the gauze d, which supports the brass cover e of the glass chimney b; and thirdly FIG. 2. Mackworth's Safety Lamp. through the conical wire gauze /, which with its frame acts as a support to the glass chim- ney 5. This conical frame throws the air on to the flame g so as to produce a more perfect combustion and a white light. This lamp burns with a steady flame in currents of air which extinguish other lamps. It is 1J Ib. heavier than the Davy, and Ib. lighter than the Clanny lamp. The outside glass does not get so hot as in the latter, and if it breaks, there is still a perfect safety lamp inside. LAMPASAS, a central county of Texas, bound- ed W. by the Colorado river and drained by the Lampasas, a tributary of the Leon ; area, 835 sq. m. ; pop. in 1870, 1,344, of whom 86 were colored. The surface is much broken, and the soil is fertile ; much of the land is well adapted to grazing. There are white sulphur springs at the county seat. The chief produc- tions in 1870 were 45,487 bushels of Indian corn and 26 bales of cotton. There were 713 horses, 20,787 cattle, 1,241 sheep, and 4,320 swine. Capital, Lampasas. LAMPBLACK, finely divided carbon, obtained by collecting the smoke produced in burning oils, fats, and resins, with a supply of air suffi- ciently reduced to prevent perfect combustion ; the aim being to consume all the constituents Lampblack Apparatus of the burning body except the carbon, and preserve as much of that as possible. Lamp- black is prepared in large quantities by the manufacturers of turpentine, from the impure resin and other refuse matters that remain after the distillation of the turpentine. These