286 Hare’s Blowpipe. 
scale without danger. 3d. The power of varying the rela- 
tive proportions of the gases so as to oxydate, or deoxydate, 
as may be desirable. ‘This power is given by the common 
blowpipe, though in a different way, and is well known to 
be very useful. 
Yo me it is ludicrous that the author should suppose any 
analogy to exist between the phenomena of the gas blow- 
pipe, and those of volcanoes. 
In order to put the gas blowpipe into operation, it is in 
dispensable that there should be hydregen and oxygen gases 
confined under moderate and equable compression, so as to 
flow out regularly from a common aperture, at which they 
may be ignited. How are these requisites to be obtained 
in nature’ Whence the pure hydrogen or oxygen? Has 
Dr. Clark, or any other person, known them to. be extri- 
cated in purity? Is not the former always carburetted or 
sulphuretted, and the latter never purer than in the atmos- 
phere? When obtained by art, fire is requisite to liberate 
oxygen, but in nature the fumes of the fire would con- 
taminate any gas which it might evolve; and it ought not 
to be forgotten that the circumstances which are favorable 
to the evolution of oxygen, are inimical to the liberation of 
hydrogen. Again, supposing the gaseous materials gene- 
rated, where is the presiding demon with the genius to de- 
sign, and skill to regulate that due admixture of them which 
the author exulis in having discovered to be necessary, and 
granting that there could be in nature any competent substi- 
tute for human agency ina process so intricate, by what 
means, in operations so rude and extensive, is that retro- 
cession of the flame to be prevented, to obviate which, in 
Operating with his minute apparatus, a capillary tube has 
been found indispensable. In subterranean caverns, the 
gaseous elements of water might create explosions, but 
could never support the permanent heat requisite to fuse an 
orifice be made smaller, and the gases mix ata greater distance from the 
place of effius, valves should be interposed in the pipes, or the gases should 
be kept under equable pressure, as itis possible that if subjected to unequal 
pressure, the gas which | Sieve presse d, may pass from one reservoir to the 
other, on leaving the cocks open accidentally. This, however, is an over- 
sight not likely to take place, as iLis so evidently accompanied. by a waste 
of the gas, that an operator will hardly be so careless as not to close the 
coeks when the flame is not wanted. Ciosing them is in fact the usual 
mode cf extinguishing the flame. 
