J'rom gas for various purposes in the Arts. Ip^ 



ordinary pressure, I expected to produce still higher heats with 

 compressed gas. A limit, however, appeared to be set to such 

 ^n experiment, by the velocity of the issuing gas, which, at 

 a certain point, never fails to blow out the flame ; but I have 

 found that when the gas is discharged with a velocity much 

 greater than what will extinguish the flame, the explosion may 

 be kept up to any extent by the small subsidiary burner, which 

 I have already described. This result removed every difficulty 

 which seemed to be opposed to the generation of high heats 

 by exploding the gases ; and I have no hesitation in saying, 

 that the portable gas lamp will become one of the most valu- 

 able instruments that has ever been presented to the arts. 

 When either the philosopher or the artisan requries a power- 

 ful heat for any specific purpose, he must kindle a fire or light 

 a furnace, and thus obtain what he wants, with much trouble 

 and expence ; but by the present method of fitting up a port- 

 able gas lamp, he can obtain the heat of a furnace in a second, 

 and extinguish it as speedily. * 



For various purposes in domestic economy such a lamp will 

 be equally useful, particularly in summer, and under circum- 

 stances where heat could not be conveniently obtained in the 

 ordinary way. 



The preceding observations furnish us with what I conceive 

 is the true theory of the common blowpipe. The intense heat 

 generated by the blowpipe is ascribed by chemists to a concen- 

 tration of the flame by the blast, — words which have no very 

 definite meaning ; but I apprehend that the heat in question 

 is the heat generated by the repeated explosions of the explo- 

 sive mixture formed by the unconsumed gas of the flame and 

 atmospheric air. 



I hope to be able to show some of the preceding experiments 

 to the Society, through the kindness of Mr Gordon, secretary 

 to the Portable Gas Light Company, who has kindly favour- 

 ed me with a lamp for this purpose, -f- 



* Iron wire was speedily melted by this lamp. 



t The above lamp, fitted up with a subsidiary burner, was exhibited at 

 the public lectures on chemistry delivered by Dr Hope and Dr Turner 

 in 1826 and 1827. 



