106 TOUCHWOOD TINDER-BOX. 



which the piston has left ; but, on the contrary, it always shew* 

 above. 3dly. There is no vapour, when the piston loses much air, 

 if the friction be ever so rapid. -Ithly. The vapour should be more 

 apparent, wli.n the pNton exerts its friction throughout the whole 

 1< n;;th of the tube, than when it is confined to a small part of its 

 upper extremity ; yet the reverse frequently happens. 5thly. 

 "XV hen the air is entirely decomposed no more vapour appears, but 

 it shows itself again, if ever so little fresh air be introduced. 



" As it was essential to ascertain whether the vapour did not 

 contain an acid principle, I fastened to the surface of the piston, 

 with a little green wax, a piece of muslin dipped in infusion of 

 litmus, and afterward dried. After twenty strokes of the piston 

 the colour was not changed. I put on a second piece of muslin 

 larger than the first, and the edges of which were loose. This was 

 burned all round, without the colour of the rest being altered. 

 La-tly, a third piece, which was wet, experienced no change of 

 colour. 



'* From these experiments it follows, that no acid principle is 

 developed ; that all ae'ri ,'orm substances, as well a common air, 

 produce a light vapour ; that no other gass, except ox)geu and 

 common air, kindles the spunk ; that oxygen produces a much 

 more powerful combustion than common air, consequently oxygen 

 act* an important part in the inflammation ; that as it can 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 con. 

 tained in the tube is decomposed by (he simple force of compres- 

 sion ; that the vapour produced is not owing to the oxygen, since 

 it shows itself equally in gasses that contain no oxygen ; that this 

 vapour is the effect of some agent common to all gasses ; and that 

 we may presume it is caloric itself, rendered visible by the sudden 

 approximation of its p,irt> in a small space, where it rises to a tern, 

 perature that is increased in the oxygen so as to kindle the spunk. 



' It sometimes happens, that the spunk is turned black without 

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

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

 s out, which is not of the same nature as the former. That 

 how 8 itself before the inflammation: this always succeeds it. That 

 is the princip'e of the inflammation : this a product furnished by 

 the combustion of the spunk, of which it has the smell." 



[Le Douvier. Desmortiers. Journ. tie Physique. 



