THE SINUSIBRA LAMP.] 



UNDULATORY FORCES. LIGHT. 



Ill 



Many forms have been given to this lamp of M. Ar- 

 gand, according to the purpose which it is intended to 

 Fig. loi. serve : thus, there is the reading or 



Cambridge lamp (Fig. 104), the well- 

 known table lamp (Fig. 105), and 

 the suspended lamp. 



(6.) The Rumford or Annular 

 TabU Lamp is an improvement on 

 the last. It was contrived by Count 

 Rumford, for the purpose of avoid- 

 ing the deep shadows which are pro- 

 duced by the reservoirs of the pre- 

 ceding ; and it became so great a 

 favourite, that even to this day it is 

 occasionally used. The oil is con- 

 tained in a hollow ring, which is 

 Ced a little below the level of the 

 e; and the cistern is fed by 

 means of two tubes, which also 

 serve as supports. In order to 

 diffuse the light still more, the 

 burner is surrounded by a ground- 

 glass shade, which almost entirely 

 conceals the ring (Fig. 106). 

 (c.) Parker's Sinumbra Lamp was patented in 1820. 

 It was called the shodowless lamp, because it did away 

 Fig. IDS. Fig. loc. 



with the slight shadow which is always perceptible in the 

 lart. The improvement is threefold : First, the annular 

 *'" reservoir is bevelled off 



rum above, so as to 

 present a very thin edge 

 on the outside ; secondly, 

 the glass is shaped in 

 such a manner as to dif- 

 fuse the light over the 

 edge of the ring, and 

 under it ; and, thirdly, a 

 conical reflector is placed 

 around the inner glass a 

 little above the flame. 

 All these arrangements 

 are represented in Fig. 

 107, which shows the lamp 

 in section. 

 fd.) Quarre?* Sinumbra Lamp (Fig. 108) is another 



In. 1 I. 



contrivance for effecting the 

 same object as Parker's ; but 

 the bevelling of the reser- 

 voir is on the under surface 

 of the ring, instead of the 

 upper; and the ground-glass 

 shade is made sufficiently 

 largs to reach to the very 

 outer edge of the ring. 



(e.) The Iris Lamp is one 

 of the most recent improve- 

 ments of the Rumford and 

 Argnnd : it differs very 

 little f.om the preceding, 

 eicept that the outer edge 

 of the annular chamber is 



reduced to a mere bead ; and the ground-glass shade 

 is not only brought to the very front of the ring, but 

 its body is formed in such a way as to bulge over it. By 

 these contrivances the shadow of the reservoir is re- 

 duced to a minimum. 



(/.) Quarrel's Albion Lamp. This marks the next 

 attempt to improve the Argand, by carrying the re- 

 servoir for the oil over the flame, and, therefore, 

 out of the way of the shadow, instead of having it, 

 in Rumford's contrivance, around it and a little 



Fig. 109. 



below it. The construction of this 

 lamp is represented in Fig. 109. 

 A is the reservoir for holding the 

 oil, which is introduced through 

 the two valve-cocks B; C is the 

 tube that conducts it to the cistern 

 D ; and F U a syphon- valve for 

 admitting atmospheric air to the 

 reservoir, so as to supply the place 

 of the consumed oil. G is a pinion 

 for regulating the height of the 

 wick. The whole is enclosed in a 

 tulip-shaped glass ; and, with the 

 exception of the side-tubes, there is 

 nothingto produce a shadow. 



(3.) Parker't Hot-oil Lamp is constructed somewhat 

 like the preceding, though a contrivance is adopted for 

 making the oil hot before it reaches the wick ; by which 

 means it becomes more fluid, and burns with greater 

 facility. Fig. 110 shows the plan of this lamp. The 

 reservoir U above the flame, and the Fig. no. 



top of the glass is fitted into an iron 

 chimney, which radiates heat very 

 freely to the reservoir. The oil 

 panes down through a lateral tube to 

 the cistern, and there is a stopcock 

 in the tube to cut off the supply of 

 oil when necessary. The wicks are 

 very short ; and instead of being ad- 

 justed by the rack and pinion, a 

 movement is given to the glass, which, 

 by its position, regulates the intensity 

 of the flame. A painted shade is put 

 over the whole, in order that the 

 reservoir may be hidden. The ad- 

 vantage of this lamp is, that it will consume the very 

 commonest oil without producing an unpleasant smell. 

 One caution, however, is necessary in the management 

 of it namely, that the reservoir be tilled quite up with 

 oil before the lamp is lighted. If this be not attciulr.l 

 to, the air contained in the chamber ill expand by the 

 action of the heat, and the oil will be forced out over 

 the wick, and will run about. 



(h.) Keif's Fountain Lamp. In all the preceding con- 

 trivances, the supply of oil to the ilaine in chiefly effected 

 by the capillarity of the wick. In some cases it is 

 assisted by the gravitation of the oil from a reservoir 

 situated above the level of the burner. But it has 

 always been thought desirable to have the reservoir in 

 the stem or body of the lamp, so that the unsightly 

 appearance of the chamber might be avoided, and the 

 shadow which it invariably cants to a greater or less 

 extent upon surrounding objects, entirely prevented. 

 This, however, can only be accomplished by means of 

 some power whereby the oil shall be pressed up from the 

 well in which it is contained, to the level of the flame. 

 " To effect this, two methods have been resorted to : one 

 is on a hydrostatic principle, in the manner of Hiero's 

 fountain, where the oil is placed in the body of the stem, 

 and is raised to the wick, as it is wanted, by the pressure 

 of a column of some fluid : in the other method, the oil 

 is forced by clock-work mechanism, as in the lamp of 

 Carcel of Paris. The first successful attempt of this 

 kind in England, was in the lamp invented by Mr. 

 Keir, about forty years ago, upon a hydrostatical prin- 

 ciple; and although it is not used at present, being 

 superseded by contrivances of a similar kind by other 

 manufacturers, yet it will serve to illustrate the general 

 n ituro of these lamps, of which several varieties have 



