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LXXIII. On a New (Economical Lamp. 

 To Mr. Tilloch. 



Sir, In the last number of Nicholson's Journal there is 

 a figure, and a long description, of an octonom'tcal lamp, by 

 L. O. C. Like Argand's lam]), it has an air tube through 

 the centre of il, and the flame is burroundtd by a glass 

 chimney; but the chimney is verv short, and the fiame 

 arises from eight small wicks that are placed at equal di- 

 stances from one another, in a circle round the air- tube. 

 The small tubes which contain the wicks are not large 

 enough in diameter to receive more th.an four threads of 

 cotton. The inventor con.pared his lamp with an Argand's 

 ]am|/j by heating a given quantity of v\aier with each, and 

 found ihcm equal in power, while his own consumed not 

 more than half so much oil as the other ! — I have had one 

 of these new lamps constructed, and with it have per- 

 formed the following experiments : 



Experbnent 1. — The two shadows of a cylinder of wood 

 were equally strong, when an Argand lamp was fourteea 

 feet, and the new lamp onlv seven feet four im hes, distant 

 from the white plane on which the shadows were exhi- 

 bited. 



Experiment 2. — A dish of water, having a thermometer 

 in it, was placed an inch above the glass chimney of the 

 Argand lamp: in 73 seconds the temperature of the water 

 was elevated from 53° to 75^. The dish, containing the 

 same quantity of v.'ater at 53'', was placed an inch above 

 the chinmev of the new lamp, and the teniperature was not 

 raised to 75° in less than 165 seconds! The chinmey of 

 the new lamp was three inches long» and thai of the Ar- 

 gand lamp four inches and a hall'. The new lamp seemed 

 to act as powerfully without the a;lass as with it. 



Expejiment 3. — Imaginiuij t,hat the wicks of the new 

 lamp might have a better effect if ranged in a smaller circle, 

 ttiey were accordmyly altered, and again used, hui this time 

 with a glass chmuiey only one inch high; for a longer 

 chinmev extinguished the lights. The two shadows were 

 equal when this lamp was eight feet one inch distant, and 

 Argand's lamp 14 feet. 



Eipeiimeiit 4. — The Argand lamp raised the tempera- 

 ture of a eiven quantity of water lo" of Fahreidieit in 58" 

 of time: the other lamp produced an equal eltvct in Tb", 

 the chimneys in both cases being placed at the same distance 

 below the dish of water. But when tlie flame of the new 



lamp 



J 



