IGNITION FROM COMPRESSED AIR. 2*27 



This was burned all round, without the colour of the rest being 

 altered. Lastly, a thu'd piece, which was wet, experienced no 

 change of colour. 



From these experiments it follows, that no acid principle is General inf«- 

 developed : that all aeriform substances, as well ascommen air, ^^^n^^^s. 

 produce a light vapour : that no other g^s, except oxigen and 

 common air, kindles the spunk : that oxigen produces a much 

 more powerful combustion than common air, consequetitly 

 oxigen acts an important part in theinflammation : that asitcan 

 exert its action only when set free by the decomposition of the 

 common air, of which it constitutes a fourth; part, it follows, 

 that the air contained in the tube is decomposed by the simple 

 force of compression : that the vapour produced is not owing 

 to the oxigen, since it shows itself equally in gasses that contain 

 no oxigen : that this vapour is the etTect of some agent com- 

 mon to all gasses : and that we may presume it is caloric itself, 

 rendered visible by the sudden approximation of Its parts in a 

 small space, where it rises to a temperature that is increased in 

 the oxigen so as to kindle the spunk*. 



I am equally induced to believe, since the air, and it is the Luminous itie- 

 same with all gasses, is decomposed by rapid compression, that teors indepen- 

 ,1. I . ^ r 1 • 1 . 1 • deiit of erectri- 



the lummous meteors frequently perceived m hurricanes are ^^^ 



not always the effects of electricity. I have observed several 

 times, on these occasions, that Saussure's atmospheric electro- 

 meter affords no signs of any. I will mention a particular in- 

 stance, as it occasioned me no less surprise than damage. 



In the beginning of the year 1803, being at my country j^^ j-j^ ^jjjjj5_ 

 seat, toward evening a violent wind arose, which continued in- 

 creasing for two hours to such a degree, as to blow down 

 about sixty trees of prodigious size and height in an ornamental 

 plantation. It threw them one upon another in a row, and 

 some of them were broken off". Those that were torn up by 

 the roots brought up the earth with them to the distance of 



* It sometimes happens, that the spunk is turned black without Vapour of a 

 kindling. In this case, as well as when it is kindled, if we draw back dinerent kinJ, 

 the piston in the tube, a dense vapour, that may be smelt, issues out, 

 which is not of the same nature as the former. That shows itself be- 

 fore the inflammation : this always succeeds it. That is the principle of 

 the inflammation : this a product furnished by the combustion of 

 the spunk, of which it has the smell. 



Q 2 fifteen 



