104 



of water, it would not give more heat than a flame of hydro- 

 gen burning in an atmosphere of oxygen, (/) and therefore any 

 mixture more than is required for the combustion i-i unnecessary. 

 The compressed state of the gases is of moreimportance ; if while 

 a jet of hydrogen were burning u\ oxygen their densities were 

 suddenly doubled, all other circumstances remaining the same, the 

 heat would be much increased, for the same quantity of caloric 

 would be evolved in half the space. But the quantity of ca- 

 loric evolved cannot be the same, for much heat is given out 

 in condensation, and this nmst be subtracted from the product 

 of combustion. Air suddenly compressed into i of its volume is 

 heated upwards of 1000°, how much more we know not ; and M 



besides this in the new blowpipe, the condensed gases are in the I 



act of absorbing heat during their ignition, for they are expand- ■ 



ing, and the escape of compressed air has been actually pro- 

 posed as a frigorific process ; and if we further consider that all 

 compression is at an end when the gases arrive at the end. of 

 the tube, or in fact before they arrive at the body to be heated, 

 we must admit that little augmentation of effect is produced 

 by it. 



Lastly, we can vary the properties of the flame at pleasure, 

 while with the new bloAvpipe the proportions of the gases are in- 

 variable during an experiment. If the common blowpipe had 

 not its oxygenating and deoxygenating flame, it would be of 

 comparatively small value to the mineralogist ; but our instrument 

 possesses both these powers in the highest degree, and it thus 



(J'J This seems to follow from the fact that hydrogen when burnt witli atmospheric- air 

 ip my blowpipe, and in the open air, had eiiual powers of fusing platina wire. 



