126 DEFECTS OF THE DAVY LAMP. CHAP. VII. 



same fact several years before, though neither Stephen- 

 son nor Davy knew it while they were prosecuting their 

 experiments. Sir Humphry Davy's subsequent modifi- 

 cation of the tube-lamp, by which, while diminishing 

 the diameter, he in the same ratio shortened the tubes 

 without danger, and in the form of wire-gauze enveloped 

 the safety-lamp by a multiplicity of tubes, was a beau- 

 tiful application of the true theory which he had formed 

 upon the subject. 



The increased number of accidents which have occurred 

 from explosions in coal mines since the general intro- 

 duction of the Davy lamp, have led to considerable 

 doubts as to its safety, and to inquiries as to the means 

 by which it may be further improved ; for experience 

 has shown that, under certain circumstances, the Davy 

 lamp is not safe. Mr. Stephenson was of opinion that 

 the modification of his own and Sir Humphry Davy's 

 lamp, combining the glass cylinder with the wire- 

 gauze, was the most secure ; at the same time it must be 

 admitted that the Davy and the Geordy lamps alike 

 failed to stand the severe tests to which they were sub- 

 mitted by Dr. Pereira, before the Committee on Acci- 

 dents in Mines. Indeed, Dr. Pereira did not hesitate to 

 say, that when exposed to a current of explosive gas the 

 Davy lamp is " decidedly unsafe," and that the experi- 

 ments by which its safety had been " demonstrated " in 

 the lecture-room had proved entirely " fallacious." 



It is worthy of remark, that under circumstances 

 in which the wire-gauze of the Davy lamp becomes red- 

 hot from the high explosiveness of the gas, the Greordy 

 lamp is extinguished ; and we cannot but think that 

 this fact testifies to the decidedly superior safety of the 

 Geordy. An accident occurred in the Oaks Colliery 

 Pit at Barnsley, on the 20th of August, 1857, which 

 strikingly exemplified the respective qualities of the 

 lamps. A sudden outburst of gas took place from the 

 floor of the mine, along a distance of fifty yards. For- 



