fast Biographical Memoir of Sir Humphry Davy. 



A single envelope of this metallic gauze, whenever employed 

 with requisite precaution, henceforth secures miners from the 

 terrible danger which threatened their lives ; air ready for ex- 

 plosion may surround their lamp without any other danger 

 than that of extinguishing it, and even then, if there be sus- 

 pended over the wick a spiral wire of platina, it will become in- 

 candescent by the decomposition of the detonating gas, and af- 

 ford light to the miner as long as there are any remains of re- 

 spirable air. 



This instrument, now used in the greater number of mines, 

 and introduced by Mr Davy himself into those of Hungary, has 

 been the means of preserving the lives of many useful men : and 

 its services would have been of even greater importance, had it 

 not been for the indifference which has prevented its adoption 

 in some countries, and negligence in observing the rules pre- 

 scribed by its inventor in others. Men's minds are usually so 

 little occupied with the thoughts of death, that the most trifling 

 present annoyance has more influence than the greatest danger 

 when it appears somewhat remote. 



It now looked as if Mr Davy might be asked to make a dis- 

 covery, adapted to the necessities of any particularj case. The 

 copper-sheathing of ships is oxidized by sea water, and in a nu- 

 merous navy like that of England, the expense of renewing it is 

 enormous. The Admiralty in 1823, asked him to suggest a 

 preservative, and he was not long in complying with their wishes; 

 he had only to refer to former discoveries to be enabled to add 

 one more to their number. 



According to his practice, he first sought to give a precise 

 account of the phenomena. Copper immersed in sea- water, pro- 

 duces a bluish-green powder, on which is deposited the carbo- 

 nate of soda, an obvious proof that the marine salt has been de- 

 composed ; but, according to his theory of muriatic acid, this 

 could not take place without oxygen, and as no hydrogen ap- 

 peared, it could not be the water that furnished this oxygen 

 but the atmospheric air which it contained. On the other hand, 

 according to his theory of the correspondence between chemical 

 action and the electrical condition of bodies, it was in conse- 

 quence of its positive electricity relatively to the salts contained 



in the water, that the copper disengaged oxygen ; it followed, 



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