MINING. 297 



Dr. Clanny made the lower part of his cylindrical envelope of 

 thick glass ; George Stephenson added a cylinder of glass inside 

 that of wire gauze, through the whole length of the lamp, and 

 introduced the air for combustion through very minute holes in 

 the rim under the glass. These types have been taken up and 

 farther modified both in this country and on the Continent, 

 with a variety of results as to the amount of light given and the 

 facility of burning. No other has given as yet so much satis- 

 faction and inspired such confidence as the Mueseler lamp, 

 principally employed in Belgium, and of late years introduced 

 into several works of the largest class in the north of England 

 and in Wales. In it a central conical chimney facilitates an 

 up and a down draught, which cause a brisk combustion and a 

 good light, and thereby remove the temptation to unscrew the 

 lamp-top. It is open, however, to two objections, viz., the passing 

 of the flame at a velocity hardly above that of the Davy, and the 

 fragility of glass, which renders good annealing and care in 

 travelling and in vertical suspension of the lamp very important 

 elements of security. 



A multitude of devices for securely locking the lamps, to 

 prevent their being tampered with, and of automatic extinguishers 

 and tell-tale detectors, have been introduced, with more or less 

 success. Thus, superior to the very common form of lock so 

 easily picked is the leaden pin put through the adjoining rims of 

 the upper and lower part of the lamp, and stamped with some 

 device when handed to the men on going to their work; and, 

 again, the magnetic lock exhibited by M. Arnould, of Mons, in 

 Paris, 1867, and now patented by Messrs. Craig and Bidder, in 

 which the top can only be taken off when the lamp is placed on 

 the poles of a powerful magnet. As for the many methods of 

 making the act of unscrewing cause the extinction of the light, 

 they are likely to be of little account as long as men can take 

 lucifers or " safety " matches in their pockets ! 



Several varieties of lamp have been brought forward since the 



