in Comlustion, and in the Condensation- of Vopours. 435 



I should detail, in order to caution those who undertake 

 the inquiry. 



When I made experiments with highly rectified alcohol, 

 and particularly with ether, I found it verv difficult to pre- 

 vent a remarkable part of these volatile liquids from escap- 

 ing in vapour from the ma»8 of the liquid which remained 

 ni the laijip. I constructfd a small lamp in the form of a 

 round tobacco box, with a beak risinc from the centre of the 

 circular piaie which forms the top : and upon this I fixed a 

 sn);'ll leservoir to con-tain cold water, intended to cool the 

 beak, and prevent the heat from descending to the body of 

 the lauip: but this precaution was not sufficient when I 

 burnt ether, as I learned to my cost. Althouoh the re- 

 servoir was twice as large in diameter as the lamp, and it 

 was filled with cold water, this water was so heated in a 

 few minutes that there was an explosion of ether in the 

 state of vapour which took fire in the open air, and burned 

 with aflame which touched the cieling, threatenino- to set 

 fire to the house. ° 



Rendered cautious by this accident, I constructed a new 

 lamp, much smaller than the former: it was only an inch 

 in diameter and ihree-fourths of an inch in depth, and its 

 beak, which was only two lines in diameter, was three- 

 fourths of an inch high. ]n order to keep this small lamp 

 conl while it was burning, it was placed in a small tub, and 

 kept constantly submerged three lines below the upper ex- 

 tremity of its beak in a mixture of water and pounded ice. 

 These precautions were sufficient to prevent explosions, 

 but did not prevent the evaporation of the ether or of 

 the alcohol. I was convinced of this fact by observing, 

 that always, when I made two consecutive experiments 

 without filling the lamp afresh, the alcohol constantly ap- 

 peared weaker in the second experiment than in the first. 



It was not difficult to account for this phaenomenon : the 

 most volatile, and consequently the most combustible parts 

 ol- this liquid being dispersed in vapours in the interior of 

 the lamp, foond means to escape at the beak, with part of 

 llie liquid which had passed through the wick, leaving the 

 alcohol which remained in the lamp sensibly weakened. 



In order to remedy this imperfection, \ constructed a 

 thud lamp, which I have presented to the Class. It is 

 made of copper, and has the form of a small cylindrical 

 vase an inch and a half in diameter, and three fourths 

 ot an inch in height, swelled a little at top and hermetically 

 closed by a stopper of copper, which btint: ground with 

 emery is wedged into the neck of the vessel." 



E e 2 This 



