'' Controversy concerning Safe-lamps." 23 



The great principle of security that Sir H. Davy discovered, is, 

 that certain cooling surfaces used for transmitting gas destroy 

 the power of communicating explosion. To this no other per- 

 son can lav claim: audit required great sagacity, and multiplied 

 and varied experiments, to trace this principle from its opera- 

 tion in long metallic tubes and canals, to that in a tissue per- 

 meable to light and air, and impermeable to flame. 



Capillary tubes or narrow canals, as Sir II. Davy has shown, 

 are not safe as such. He has demonstrated that their power of 

 preventing the passage of explosion depends upon their number: 

 nor are numerous small apertures safe, unless they exist in a 

 whole surface. The explosion of hydrogen, it is well known, will 

 pass through an aperture of l-70tii of an inch in diameter, or 

 through a glass tube l-40th of an inch diameter and six inches 

 long. 



Mr. R. W. Brandling is of opinion that wire-gauze is only the 

 extremities of capillary tubes : — this opinion is too ridiculous to 

 merit serious notice. It is singular that Mr. R. W. Brandling 

 has not discovered the principle of the wire-gauze safe-lamp in 

 the common wire firescreen. According to such analogical 

 reasoning, the steam-engine would be only the prolongation of 

 a teakettle, and the air-pump an improvement of the wet leatlier 

 used by children for raising smooth stones. 



I know from very good authority that Mr. R, W. Brandling 

 was present when a vote of thanks was unanimously passed to 

 Sir H. Davy by the coal trade, for his brilliant discovery of the 

 wire-gauze safe-lamp: nor did he set up any claims for Mr. 

 Stevenson till some months after, when a present of plate was 

 in contemplation : — and it should be published for the honour of 

 the coal owners, that on this occasion his was the only disputant 

 voice. 



Mr. R. W. Brandling is himself the constructor of a rival 

 lamp, and on such an occasion he cannot be regarded as a very 

 unprejudiced advocate, or even witness ; and, except to those 

 who are very ignorant of the most common principles of che- 

 mistry, there can be no question of analogy between the at- 

 tempts of .Mr. Stevenson, as they have been justly called by the 

 committee of the coal trade (however Kiudablej, and the scientific 

 discoveries of Sir H. Davy. 



Mr. G. Stevenson may (as Mr. Hodgson says in his candid 

 and gentleman-like communications) be a very modest and in- 

 genious man. As an engine-wriglit I dare say he is superior to 

 most who exercise that occupation ; and Mr. R. VV. Brandling 

 can only do harm to a ut^eful and industrious mechanic, by per- 

 suading him to set up as a philosophical discoverer. 



It cannot seem extraordinary to any one who has considered 



the 



