ON THE HEAT DEVELOPED IN COMBUSTION. ]21 



high. To keep this small lamp cool while burning, it was 

 placed in a small pan, and kept constantly immersed in a 

 mixture of water and pounded ice to within a quarter of an 

 inch of the extremity of the nozzle. These precautions were This prevent- 

 sufficient to prevent any explosion, though not the evapora- f d explosion, 

 tion either of the ether or of the alcohol. This fact I learned ration, 

 from observing, that, as often as I made two consecutive ex- 

 periments without filling the lamp afresh, the alcohol con- 

 stantly appeared weaker in the second experiment than in 

 the first. 



The cause of this phenomenon was not difficult to disco- 

 ver. The most volatile, and consequently the most combus- 

 tible parts of this liquid, being diffused in vapour in the in- 

 terior of the lamp, found means of escaping through the 

 nozzle with the part of the liquid that traversed the match, 

 leaving the alcohol, that remained in the lamp, perceptibly 

 weakened. 



To remedy this imperfection I constructed a third lamp, A third lamp 



which I now submit to the inspection of the class. Tt is made that s " cc f ded 



r . . completely. 



of copper, and has the shape of a small cylindrical vase, an 



inch and half in diameter, and three inches high, swelling 



out a little atop, and closed hermetically by a copper stopple, 



which, being ground with emery, fits tight into the neck of 



the vase. Through the centre of this stopple passes a small 



perpendicular hole, which can be shut completely, or left a 



little open, as may be required, by means of a small screw 



carrying a copper collar. 



A small tube, about an eighth of an inch in diameter and 

 two inches and half long, proceeds horizontally from the side 

 ofthe vase very near the bottom. At the distance of an inch 

 and four lines from the vase this tube is bent at a right angle, 

 rising upwards perpendicularly to form the nozzle of the 

 lamp. 



This little tube is every where very thin, except at its 

 upper extremity, where it is made thicker, to admit of being 

 shaped so as to fit tight into a very small cylindrical extin- 

 guisher, 5 lines high by 3-5 in diameter ; intended to close 

 the nozzle hermetically without touching or deranging the 

 wick, the moment the lamp ceases to burn ; and to keep \t 

 constantly closed, when the lamp is not lighted. 



Without 



