390 On the Heat developed in Combustion 



lamp ceases to burn, and to keep it constantly closed 

 when the lamp is not lighted. 



Without this precaution, in experiments made with 

 ether, so large a quantity of this volatile liquid would 

 evaporate through the nozzle of the lamp while weigh- 

 ing, that it would be impossible to ascertain the quantity 

 burned. 



The nozzle of the lamp is steadied by two pieces of 

 wire, proceeding from it horizontally, and soldered to the 

 body of the lamp. 



To keep this lamp constantly cold, as well as the 

 liquid it contains, it is placed in a small pan, and covered 

 completely, except the extremity of its nozzle and that 

 of its neck, with a mixture of pounded ice and water. 



When the lamp is weighed, it is taken out of the pan, 

 and well wiped with a dry cloth before it is put into the 

 scale. 



When the lamp is kindled, the operator must not for- 

 get, after it has burned two or three minutes, to open 

 the screw that closes its stopple a little, though but 

 'very little, otherwise it might go out. 



As the little horizontal tube, by which the liquid that 

 is burned passes from the reservoir of the lamp to its 

 nozzle, is always filled with liquid, so 'that it can have 

 no communication with the vapour diffused in the upper 

 part of the reservoir, this vapour cannot escape by the 

 nozzle of the lamp, as it did before I thought of this 

 method of preventing it. 



If I have been very minute in my description of this 

 lamp, it is because I thought it necessary to spare those 

 who might be disposed to repeat my experiments, or make 

 similar ones, all the difficulties I had to surmount before 

 I found the means of having under command the com- 

 bustion of very volatile inflammable liquids. 



