732 SAFETY LAMP 



at the moment when required. They are also aware that a great inconvenience, not 

 to say danger, has been introduced by all those hitherto employed, in consequence 

 of the apparatus being brought into play by a plunge during the rapid descent of the 

 cage, and that hence several of those inventions, after being fairly tried for one, two, 

 or three years, have been ultimately removed. Nor is it too much to say, although 

 an insufficient argument if taken alone, that the employment of this apparatus has 

 a tendency to make people careless about the examination and renewal of ropes.' 



SAFETY ruSE. A woven cylinder containing gunpowder, employed in blasting 

 rocks, especially in our mines. The safety fvfse is also prepared for blasting under 

 water. See FUSE, SAFETY. 



SAFETY XiAIKP. The dangerous nature of the accumulation of fire-damp in a 

 colliery renders it necessary that some means should be employed to produce light 

 under such circumstances that the risks of explosion are greatly reduced. 



The contrivance of a steel mill was formerly used, but it afforded only a gleam of light. 



It consisted of a small frame of iron, mounted with a wheel and pinion, which gave 

 rapid rotation to a disk of hard steel placed upright, to whose edge a piece of flint was 

 applied. The use of this machine entailed on the miner the expense of an attendant, 

 called the ' miller.' Nor was the light altogether safe, for occasionally the ignited 

 shower of steel particles attained to a sufficient heat to inflame the fire-damp. 



At length the attention of the scientific world was powerfully attracted to the means 

 of lighting the miner with safety, by an awful catastrophe which happened at Felling 

 Colliery, near Newcastle, on May 25, 1812. This mine was working with great vigour, 

 under a well-regulated system of ventilation, set in action by a furnace and air-tube, 

 placed over a rise-pit in elevated ground. The depth of winning was above 100 

 fathoms ; 25 acres of coal had been excavated, and one pit was yielding at the rate of 

 1,700 tons per week. At eleven o'clock in the forenoon the night shift of miners was 

 relieved by the day shift ; 121 persons were in the mine, at their several stations, 

 when, at half-past eleven, the gas fired, with a most awful explosion, which alarmed 

 all the neighbouring villages. Of the 121 persons in the mine at the time of the ex- 

 plosion, only 32 were drawn up the pit alive, 3 of whom died a few hours after the 

 accident. Thus no less than 92 valuable lives were instantaneously destroyed by the 

 fire-damp. 



Dr. W. Reid Clanny, of Sunderland, was the first to contrive a lamp which might 

 burn in explosive air without communicating flame to the gas in which it was plunged. 

 This he effected, in 1813, by means of an air-tight lamp, with a glass front, lie flame 

 of which was supported by blowing fresh air from a small pair of bellows through a 

 stratum of water in the bottom of the lamp, while the heated air passed out through 

 water by a recurved tube at top. By this means the air within the lamp was com- 

 pletely insulated from the surrounding atmosphere. This lamp was the first ever 

 taken into a body of inflammable air in a coal-mine, at the exploding point, without 

 setting fire to the gas around it. Dr. Clanny made another lamp upon an improved 

 plan, by introducing into it the steam of water generated in a small vessel at the top 

 of the lamp, heated by the flame. The objection to these lamps was their inconveni- 

 ence in use. 



In the course of a long and laborious investigation on the operation of the fire- 

 damp, and the nature and communication of flame, Sir H. Davy ascertained that the 

 explosions of inflammable gases were incapable of being passed through long narrow 

 metallic tubes ; and that this principle of security was still obtained by diminishing 

 their length and diameter at the same time, and likewise diminishing their length 

 and increasing their number, so that a great number of small apertures would 

 not allow an explosion to pass, when their depth was equal to their diameter. This 

 fact led him to trials upon sieves made of wire-gauze, or metallic plates perforated with 

 numerous small holes ; and he found that ignited gases would not pass through them. 



The apertures in the gauze should never be more than ^th of an inch square. In 

 the working models, eent by Sir H. Davy to the mines, there were 7*8 apertures in 

 the square inch, and the wire was about ^th of an inch diameter. The cage or 

 cylinder of wire-gauze should be made by double joinings, the gauze being folded 

 over in such a manner as to leave no apertures. It should not be more than 2 inches 

 in diameter, or in large cylinders the combustion of the fire-damp renders the top 

 inconveniently hot ; and a double topis always a proper precaution, fixed at a distance 

 of about half an inch above the first top. 



The principles upon which these lamps are constructed, dependent as they are upon 

 some of the most refined researches of science, must be briefly described. Flame is 

 gaseous matter in a state of combustion, that is, it is under the ordinary circumstances 

 carburetted hydrogen gas in active combination with oxygen. During the intense 

 chemical action there is u great increase of volume, carbonic acid and water- vapour 

 escaping. Fire-damp is for the most part light carburetted hydrogen or marsh-gas. 



