On the Discovery of the Safe-lamp . 29 



difference of their velocity in the planes which they traverse, 

 and the diversity in the mixture of the rays forming the spec- 

 trum. 



I am, sir, 



Your very ouedient servant, 



Wvcombe^ec^O. 1816. ' ^^""^^^^ "°^^:i, 



V Oil Mr. George Stevekson's Pretensions to the Discovery 

 of the Safe-lamp. By A Correspondent. 



To Mr. Tilloch, 



Sir, — I PRESUME, when you say in the last 'number of the 

 Philosophical Magazine that "you had conceived that Mr. George 

 Stevenson's and Sir H. Davy's discoveries were made mdepen- 

 dent of each other, that you mnst allude to Sir H. Davy's first 

 lamp, with apertures in the bottom and top ; for I cannot sup- 

 pose that vou can mean to establish an analogy between Sir H. 

 jiavy's wire-gauze safe-lamp, and any thing that Mr, G. Steven- 

 son has attempted, . , , 



The only date of Mr. G. Stevenson's that can be considered as 

 of anv value, is that of Nov. 24, which is more than a fortnight 

 after Sir H. Davy's first paper, and a week after his second paper 

 had been read to the Royal Society, and twenty days after Sir 

 H Davy's discovery had "been made known to the coal-trade, 

 and a month after it had been stated publicly to the Chemical 

 Societvof London, " that if a lamp was supplied with air through 

 •»mall apertures only, below, explosive atmosphere would extin- 

 guish the flame," 'and " that explosive atmospheres could not 

 transmit the explosion through small tubes." 



Mr. G. Stevenson says, that he only profited m the practice 

 of his lamp by the publications of scientific men ; and it is jjretty 

 evident, from the circumstances of dates, that he profited by what 

 Sir H. Davy had published, though certainly the profit was very 



Mr. G, Stevenson is said to have embraced the idea of ad- 

 mitting h'vdrogen in small quantities, so as to consume it by com- 

 bustion, and this in a close vessel. Nothing can be more ab- 

 surd than the idea. He attempted this with a tube and a slider 

 as late as Nov. 17, long after Sir H. Davy had shown and pub- 

 lished that capillary tubes, of a certain diameter and m certain 

 numbers, were safe, and that a lamp supplied with air through 

 small apertures in the bottom was safe. 



Mr. G. Stevenson's friends at first were very anxious to show 



that his lamp was not stolen from Sir II. Davy's. When, on 



Nov. y. Dr. Grey and the Rev. J. Hodgson spoke oi Sir 1 1. Davy s 



^ discoveries. 



