SAFETY LAMP. 169 



The Autumn of 1815 is rendered memorable by the discovery of this 

 lamp, one of the most beneficial applications of science to economical 

 purposes ever invented. "Davy," says his biographer, " was led to the 

 consideration of this subject by an application from Dr. Gray, now 

 Bishop of Bristol, the Chairman of a Society established in 1813, at 

 Bishop Wearmouth, to consider and promote the means of preventing 

 accidents by fire in coal pits. Being then in Scotland, he visited the 

 mines on his return southward, and was supplied with specimens of fire 

 damp, which, on reaching London, he proceeded to analyze. He soon 

 discovered that the carburetted hydrogen gas, called 'fire damp' by the 

 miners, would not explode when mixed with less than six, or more than 

 fourteen times its volume of air ; and further,that the explosive mix ture could 

 not be fired in tubes of small diameters and proportionate lengths. 

 Gradually diminishing these, he arrived at the conclusion that a tissue 

 of wire, in which the meshes do not exceed a certain small diameter, 

 which may be considered as the ultimate limit of a series of small tubes, 

 impervious to the inflamed air, and that a lamp covered with such tissue 

 may be used with perfect safety even in an explosive mixture, which 

 takes fire and burns within the cage, securely cut off from the power of 

 doing harm. Thus, when the atmosphere is so impure that the flame of 

 the lamp itself cannot be maintained, 'the Davy' still supplies light to 

 the miner, and turns his worst enemy into an obedient servant". This 

 invention, the certain source of large profit, he presented with character- 

 istic liberality to the public. The words are preserved, in which, when 

 pressed to secure to himself the benefit of it by patent, he declined to do 

 so, in conformity with the high-minded resolution which he formed upon 

 acquiring independent wealth, of never making his scientific eminence 

 subservient to gain. "I have enough for all my views and purposes, 

 more wealth might be troublesome, and distract my attention from those 

 pursuits in which I delight. More wealth could not increase my fame 

 or my happiness. It might, undoubtedly, enable me to put four horses 

 to my carriage ; but what would it avail me, to have it said, that Sir 

 Humphrey drives his carriage and four?" And such was the man the 

 philosopher whose monument we look for in vain at Westminster Abbey, 

 because his widow would not submit to "Priestly extortion !" 



