11' I 



DNDULATORY FORCES. LIGHT. 



[AROAND OIL-LAMPS. 



used by the Esquimaux, who employ a wick of dry 

 Mi 



(6.) The Common Street Lamp (Fig. 91) was onco to be 

 i - . Pig. 



'J 



seen at the stalls of poor tradesmen ; though it is now 

 almost entirely displaced by the common naphtha lamp. 

 It is a tin vessel, with one or two spouts emerging from 

 the sides close to the bottom. These are packed pretty 

 tightly with cotton wick ; and being constructed on the 

 principle of the bird-fountain, the oil flows very freely 

 to the top of the wick, but does not run over. 



(c.) The Fountain Lamp (Fig. 92) is constructed on 

 nearly the same plan as the last ; and, as the reservoir for 

 the oil is above tho level of the wicks, the flame burns 

 with the same brilliancy as long as any oil remains. 

 (d.) The Common Domestic Lamp (Figs. 93 and 94) is 

 rig. 9S. made to fit a candlestick. It is a very eco- 

 nomical lamp ; though, from the circum- 

 stance that the flame is situated at a 

 considerable distance above the level of the 

 Fig. 94 oil, there is some diffi- 



culty in getting tho lamp 

 to burn when the oil 

 is at all thick, or when 

 the wick is clogged by 

 age. 



2. Common Lamp with 

 a Glass or Shade. Most 

 of the preceding may be 

 improved by surround- 

 ing the flame with a glass, 

 to keep off the currents of 

 atmospheric air, which cause the light to flicker. The 

 principal of these are represented in Figs. 95, 96, and 97 ; 

 and to the same category belong the floating night-lights 

 (Figs. 98 and 99), which are either pieces of waxed wick 

 supported on strips of tin, and kept floating by means of 

 cork, or else little caps of thin brass, pierced with a hollow 

 glass tube, in which the oil rises and burns. The safety- 

 lampof theminer(Fig. 84)*isnothing more than acommon 

 lamp, the flame of which is surrounded by a shield of 

 wire gauze ; and in the lamp of Upton and Roberts there 

 is an additional shield of glass. Fig. 97. 



3. Common Lamp, with Oxy- 

 dator. It is found that when 

 a current of atmospheric air in 

 made to impinge on the flame of 

 a common lamp, the light is 



n*M. 



rig. 96. 



much more steady and brilliant. Various contrivances 

 have, therefore, been adopted for the purpose of effecting 

 this ; as, for example, the bending in or contracting of 

 the glass immediately around the flame (Fig. 100) ; or the 

 fixing of a metal or mica disc around it (Fig. 101) ; or, 

 better still, the dropping of a perforated nipple over the 

 flame, as is seen in Fig. 102. The last constitute 



Sft antr, p. !I2. 



of the solar lamp, to which we shall have occa- 

 sion it' n-f IT I'V-and-by. It was, we believe, tirst con- 

 trive! 1>y .Mr. Koberts, the miner, and was applied to 

 his form of the unproved Davy. 



It will bo evident, on inspecting the different lamps we 

 have yet described, that the air supplied has access only 

 to the exterior of the flame. Hence the interior of the 

 flame is necessarily cooler than the exterior, and there- 

 fore tends to diminish the intensity of the whole light 

 produced. This effect may be well noticed in a common 

 tallow candle, when the wick has been allowed to burn 

 for a long time without being snuffed. If, however, a 

 supply of air could bo afivrded in the centre, the light 

 would l>e at once increased. A patent was taken out for a 

 plan of this kind, applicable to candles; but it was never 

 extensively adopted. It was on the same principles as 

 those on which the following lamps are constructed. 



4. The Aryand Lamp. This Fig. 98. 

 differs from all others, in tho 

 circumstance that the wick as 

 well as the flame, is hollow; 

 and it is so contrived that a 

 current of atmospheric air plays 

 on both sides of the flame, and 

 so increases its brilliancy. There 

 are several modifications of this 

 lamp, of which the following 

 are the most important : 



(a.) Common Aryand Lamp (Fig. 103), which consists 

 of a vase, a, to hold the oil ; a cistern, 6, to supply the 

 burner; and an arrangement, c, for adjusting the hollow 

 Fig. 100. Fig. 101. Fig. 102. 



Fig. 103. 



wick, and allowing a supply of atmospheric air on both 

 sides of the flame. The oil is put into the vase a, by 

 unscrewing it from 6, and then running in the oil through 

 the hole d, or else through the aperture in the bottom, 

 which is usually closed by the plug/. The hole d is 

 then closed by drawing up the handle g, which communi- 

 cates with a sliding tube h, and the vase is returned to 

 its place on 6. When tho lamp is lighted, the handle g 

 is to be depressed : this causes the oil to escape through 

 the hole d into the cistern 6 ; and from this it runs by 

 the side tube i t into the 

 conical chamber o, which 

 contai ns the w ick n. This 

 chamber consists of two 

 tubes, k k, II, one within 

 the other, and joined at 

 mm, so as to make a 

 closed receptacle for the 

 oil In this receptacle 

 the wick n plays freely 

 up and down; and it is 

 kept constantly im- 

 mersed in oil, as high as 

 tho aperture d, in the cis- 

 tern 6. p is a cup ]>la< -rd 

 at the bottom of the 

 chamber to receive any 

 oil that may run over 

 from the wick. Atmo- 

 spheric air rises freely 

 through c into the centre J 

 of tho flame, and it also \_ 

 blows upon the exterior 

 of it: the cause of the 

 eurrerit of air is the glass chimney which rents ou the 

 top of the burner. 



