362 THE APPLICATIONS OF PHYSICAL FORCES. [BOOK iv. 



inflammation of fire-damp. The miner's lamp which bears his name, 

 has received various modifications and improvements since its first 



invention, but the principle of its con- 

 struction remains the same. 



Figures 246, 247, 248, show several 

 patterns. In all of them the explosion 

 that would result from the introduction 

 of an explosive mixture into the chamber 

 where 'the lamp is burning is confined 

 to that chamber itself. The envelope or 

 metallic wrapper prevents the heat from 

 being able to propagate itself outwards, 

 and the miner is warned of his danger 

 without having to surfer its terrible 

 effects. 



The new patterns of Davy's lamp 

 give more light than the earlier ones, 

 as the light burns in a glass tube. 

 Moreover a particular arrangement prevents the imprudent conduct 

 of the miners in opening these lamps, as they cannot do so without 



FIG. 246. Davy's first safety lamp, 

 with cage. 



FIG. 247. Miner's safety lamp, with cage and glass tube. 



extinguishing it. The Combe lamp, which is represented in Fig. 248, 

 is formed of a thick cylinder of glass surrounding the, flame, above 



