234 



IGNITION BY COMPRESSED AIR. 



mentions the alkalis as being probably metallic sul)3tances^ 

 and those of baron Born, appear to include in a general 

 way all that the researches of Davy have realised by the 

 skilful management of an agent, the chemical power and 

 habitudes of which were discovered and extensively applied 

 in this country within a few weeks after the knowledge of it 

 was transmitted to us by Yolta, oiie of the patriarchs of elec-? 

 trical knowledge and invention. It is no derogation to the 

 merits of Davy, that he has explored the processes of na- 

 ture by simplicity of investigation, and clear deductions 

 grounded upon a knowledge of the anticedent analogies, to 

 which he has put in no claim, and upon which it is prc^b^ble 

 he may not at present set any high value. 



XVI. 



Remarks on Ignitio)i hi/ cumpressed Air. In a Letter from 

 J. A. De Luc, Esq. 



To Mr. NICHOLSON. 

 SIR, Windsor, I5th Oct. 1808. 



l^ttion by JL HAVE found in your No. 89, the following article: 



compressed n Q^ggtion respecting the ignition of Tinder by coinpressed 



" Airy In this question, as well as in the reply, the igfwi- 



tion is supposed an effect of the compression of the air 



itself; and this is the object on which 1 take the liberty of 



addressing to you some remarks. 



Theair not That this effect is not produced by the compression of air, 



Hiiich con- is proved by some circumstances of the operation; for ia 



pSton does not ^'^^^^ ^he air does not arrive to a great density in the instru- 



vccoil. ment. If the original quantity of air remained sensibly in 



the barrel; when the piston is let free, it would recoil as 



much as it has been forced in, which is far from being the 



case. A great part therefore of that air, is forced out in 



the operation ; and this even is necessary to the effect, for, 



if the piston did not reach almost the bottom of the syringe, 



the ignition of the tinder would not take place ; and such a 



motion would be impossible, did all the air, or its greatest 



part, remain in the barrel. 



It 



