202 THE FIRE-DAMP'S FAMILY CIRCLE. 



gradually lowering it down upon the wick, the taper may 

 absolutely be extinguished. Why is this? Because flame 

 is gaseous matter heated to incandescence, and the wire ring 

 cools it below the point at which incandescence is possible. 

 On the application of this principle does the safety-lamp de- 

 pend. It merely consists of a lamp-wick surrounded by a 

 layer of wire gauze, the meshes of which, through giving free 

 ingress and egress to the air, are supposed to cool flame below 

 the degree of temperature at which flame is possible ; so that, 

 however much the fire-damp may ignite and rage within the 

 wire-sheathing, its flame is unable to communicate with the 

 great reservoir of fire-damp without. 



Is theory borne out ? is Davy's lamp absolutely, function- 

 ally safe ? are the questions to be considered. To deal fairly 

 with the memory of Davy, it is necessary to make a distinc- 

 tion between accidents originating with functional derange- 

 ment of his lamp, and accidents caused by the latter in its 

 most perfect condition. No one doubts that if the wire 

 gauze of a Davy be broken or punctured, it is no longer safe ; 

 and however prone to such accidents the instrument may be, 

 they must not be imputed to inefficiency of the lamp itself. 

 To accidental derangements must be added what may be 

 termed criminal abuses ; such as removing the safety-sheath 

 for the purpose of getting more light, of sucking the flame 

 through the wire gauze by a tobacco-pipe, of thrusting a 

 pointed wire through the gauze, there to become red hot, and 

 withdrawing it to fire a charge of gunpowder. From each 

 and all these causes accidents have arisen, and they in no 

 way deserve to be laid to the charge of the lamp itself. 



Functionally, I believe the lamp to be absolutely safe, 

 except under one of two sets of conditions : what the first set 

 of conditions are, will be most conveniently illustrated by 

 the testimony of Mr. Buddie before the House of Commons 

 Commission of 1835. 



In answer to the question whether he had ever performed 



