114 



UNDULATORY FORCES. LIGHT. 



[OUAL (1AH. 



f. 1JJ. 



I e. Oft 



effects the vaporisation of the liquid, and onuses the gas 

 to escape through throe little holes at its bane; / is the 

 collar for holding the glass; and g is a handle for turn- 

 in- tin- liquid i)ll" or on. When the lamp is to be lighted, 

 it is fillod uj> with mixed spirit ; and the glass being re- 

 moved, the handle gr is to bo tunied from the left to the 

 right. A ring of wire gauze, saturated with the spirit, 

 is then lighted and brought down over the cap d, as 

 low as r. This is to bo kept burning until the metal 

 cap and chamber are sufficiently heated to generate gas, 

 which will escape through the holes and take fire. 

 \Vhen this has occurred, the glass is to be replaced, and 

 the t'lirniug jots will keep up the desired temperature. 

 Instead of turpentine and alcohol, a mixture of equal 

 parts of spirits of wine and coal-naphtha, or even coal- 

 naphtha itself, may be used. The disadvantages of the 

 lamp are its liability to go out with the least draught of 

 air. and its danger of exploding. 



(d.) The Common Xaphtha Lamp is now extensively 

 employed by poor tradespeople who keep their stalls 



out of doors. The 

 construction of 

 this lamp will be 

 understood from 

 Fig. 122: a ia the 

 reservoir for the 

 naphtha, from the 

 bottom of which 

 there passes a 

 tubeft, which sup- 

 plies the fluid to 

 the burner c. A 

 stopcock is in- 

 serted into the 

 middle of the 

 tube, in orderthat 

 the supply of 

 naphtha may be regulated, or even cut off altogether, 

 when it is not wanted at the burner. Fig. 123 exhibits 

 the construction of the latter : the naphtha enters by 

 the tube a, and it flows out of a small hole which is in 

 the lower arch of the burner, and trickles down into a 

 small cup 6 ; here it is lighted, and soon the combustion 

 of the naphtha produces so much heat that it makes the 

 whole body of the burner very hot. This causes the 

 naphtha to assume the form of vapour or gas ; and as it 

 issues out of the small hole, it is forced up against the 

 bottom of the disc c ; and thence it comes spreading out 

 in a star-like form all round the burner. This form is 

 given to it by the little breaks of perpendicular wires 

 which descend from the bottom of c ; another small disc 

 is placed below this to prevent the flame from bounding 

 back upon the jet whence it issues from the tube ; d is a 

 small wire, which is withdrawn when the interior of the 

 burner wants cleaning. 



(e.) Beetle's Naphtha Lamp. This form of lamp was 

 invented some years ago by Mr. Beale, of London : it 

 rig. m. consists of a vessel a (Fig. 124), in 



which the naphtha is placed ; thence 

 it flows by a lateral tube into the cup- 

 shaped cistern ft, and it is prevented 

 from overflowing by reason of its being 

 constructed in the same way as a bird- 

 fountain. A tube c passes up through 

 the bottom of the cistern, and reaches 

 a little above the level of the liquid : 

 this tube is placed in communication 

 with a reservoir or gasometer contain- 

 ing air. Lastly, a brass cap d, having a hole in the 

 top, is placed upon the cistern ; the lamp is put into 

 action by removing the cap and setting fire to the naph- 

 tha ; air is then blown through the tube e, and the cap 

 is gradually brought down into its place in the cistern, 

 care being taken that it is sufficiently heated during its 

 descent to keep up the volatilisation of the naphtha. 

 When this is properly managed, the air which passes 

 through the tube e carries with it so much naphtha 

 vapour as to become inflammable, and burns with a 

 brilliant jet of flame. 



ive not thought it necessary to give a description 

 of the different ornamental contrivances for setting up 

 and supporting lamps, A-c. as, for example, candle- 

 sticks, candelabra, chandeliers, <tc. ; for this would entail 

 a very elaborate account of the principles of ornamenta- 

 tion, which is not suited to the object of this work. 



ON GAS. 



General Remark* Long before gas was manufactured 

 artificially, it was generated in the great laboratory of 

 nature by the action of terrestrial heat on large accumu- 

 lations of vegetable matter, as beds of coal The pro- 

 ducts of this action made their way to the surface of the 

 earth, and escaped in the form of gas and petroleum ; 

 both of which are highly inflammable. The fires thus 

 generated, commanded attention at a very early period, 

 and altars dedicated to the gods were erected over them. 

 At the time that the Persians, under the command of 

 Mardonius, overran Greece, there were innumerable 

 altars lighted up in this manner; and so much were 

 they reverenced by the Greeks, that when the Persians 

 were defeated at the battle of Platsea, and driven from 

 the country, the two victorious generals, Pausanias and 

 Aristides, were directed by the Oracle of Delphi to build 

 an altar to Jupiter, their deliverer, and not to offer any 

 sacrifice upon it until they had extinguished all the 

 fires throughout the country which had been polluted by 

 the Persians, and had relighted them with the sacred 

 fire from Delphi. In Plutarch's Life of Alexander, we 

 are told, that when that monarch arrived at Ecbatana, 

 "he was particularly struck with a gulf of fire, which 

 streamed continually, as from an inexhaustible source. 

 He admired also a stream of naphtha not far from the 

 gulf, wlu'ch flowed in such abundance that it formed a 

 lake. The naphtha in many respects resembles bitumen, 

 but it is much more inflammable ; before any fire touches 

 it, it catches light from a flame at some distance, and 

 often kindles all the intermediate air. The barbarians, 

 to show the king its force and the subtlety of its nature, 

 scattered some drops of it in the street which led to his 

 lodgings ; and standing at one end, they applied their 

 torches to some of the first drops, for it was night. The 

 flame communicated itself swifter than thought, and the 

 street was instantaneously all on fire. " 



For several thousand years the Chinese province of 

 Se-tschuan has been celebrated for the quantity of in- 

 flammable gas that issues from the earth ; and it has 

 been stated, that the gas which escapes from the 

 ground in the neighbourhood of Pekin, is collected by the 

 inhabitants, and used for lighting the streets and houses. 

 The holy fires of Baku, near the Caspian Sea, have a 

 similar origin ; and jets of inflammable air are evolved 

 at Pietra Mala, not far from the road between Florence 

 and Bologna; at Maina, which is a few miles from 

 Modcna ; at Lycia, in Asia Minor ; and at the Artesian 

 wells of Lichweg, in Schauenburg. In this country the 

 gas is abundantly produced from the fissures of coal 

 mines, where it is known by the name of fire-damp ; and 

 it is also evolved from stagnant pools, when it is termed 

 marsh gas. At the village of Wigrnore in Herefordshire, 

 inflammable gas has on several occasions escaped from 

 the earth to such an extent, that it has been made the 

 means of lighting the neighbourhood. The same has 

 been the case at Charlemont in Staffordshire, ami at a 

 place near Glasgow. Not long since, a considerable 

 jet of gas was discharged from the Chat Moss, near to 

 the Manchester and Liverpool Railway, and it was used 

 by a neighbouring farmer for the purpose of working a 

 small steam-engine. In the village of Fredonia, in the 

 state of New York, the gas issues from the earth in such 

 abundance, that the inhabitants collect it, and employ it 

 for lighting the streets. 



History of Oat Lighting. It would naturally be sup- 

 posed that facts like the preceding would, at a very 

 early period, have commanded the attention of practical 

 men of science, and that some effort would have been 

 made to imitate the process which they saw going on in 

 uuture. Some, indeed, have thought that the ancient 



