2(j On ifie Combustion of explosiue Mixtures. 



produced by this cause, assisted by a dilution of the explosive 

 mixture. 



If a piece of wire-gauze sieve is held over a flame of a lamj; 

 or of coal gas, it prevents the flame from passing it, and the 

 phaenomenon is precisely similar to that exhibited by the wire- 

 gauze cylinders; the air passing through is found very hot, for 

 it will convert paper into charcoal ; and it is an explosive mix- 

 ture, for it will inflame if a lighted taper is presented to it ; but 

 it is cooled below the exjilosive point by passing through wire"? 

 even red hot, and by l)eing mixed with a considerable quantit} 

 of air comparatively cold. The real temperature of visible flame 

 is perhaps as high as any we are acquainted with. Mr. Ten- 

 nant was in the habit of showing an experiment, which demon- 

 strates the intensity of its heat. He used to fuse a small fila- 

 ment of platinum in the flame of a common candle ; and it is 

 proved by many facts, that a stream of air may be made to ren- 

 der a metallic body white hot, yet not be itself luminous. 



A considerable mass of heated metal is required to inflame even 

 coal gas, or the contact of the same mixture with an extensive 

 heated surface. An iron wire of -^l of an inch and eight inches 

 long, red hot, when held perpendicularly in a stream of coal gas, 

 did not inflame it, nor did a short wire of one sixth of an inch 

 produce the cifect held horizontally; but wire of the same size, 

 when six inches of it vvere red hot, and when it was held per- 

 pendicularly in a bottle, containing an explosive mixture, so 

 that heat was successively communicated to portions of the gas, 

 produced its explosion. 



A certain degree of mechanical force which rapidly throws 

 portions of cold explosive mixture upon flame, prevents explosions 

 at the point of contact: thus on pressing an explosive mixture: 

 of coal gas from a syringe, or a gum elastic bottle, it burns onlv 

 at sonic distance from the aperture from which it is disengaged. 



raking all these circumstances into account, there appears no 

 difficulty in explaining the combustion of explosive mixtures 

 within and not without the cylinders ; for a current is establishes 

 from below upwards, and the hottest part of the cvlinder i: 

 where the results of combustion, the water, carbonic acid, or 

 azote, which are not inflammable, pass out. The gas which 

 cjiters is not sufficiently heated on the outside of the wire, to be 

 exploded; and as the gases are no where confined, ther« can be 

 no mechanical force pressing currents of flame towards the same 

 point. 



It will be needless to enter into further illustrations of the 

 theoretical part of the subject : and I shall conclude this paper 

 by stating what I am sure will be gratifying to the Society, that 



the 



