136 Hydrostatic Blowpipe. 
atter can, by means of it, in a few minutes, subject small por- 
tions of any substance, to intense heat ; and is thus enabled 
to judge of the advantage to be gained, and the method to 
be pursued, in operations on a larger scale. It is by means 
of the blowpipe, that glass tubes are most 2 ead ex- 
sed to the heat necessary to mould them into the many 
forms occasionally required, for philosophical camel ; 
by the various application of tubes, thus moulded, ingenuity 
is often enabled i 
the greatest merarte to the attainment of skill, in sabe? 
tal phil 2 
“To all the pupae which I have mentioned; the blo 
pipe is fully adequate, when properly supplied as air; oi 
applied to a proper flame: but it appears that means 
which have hitherto been employed to accomplish anol ends, 
are, more or less, defective 
“The most general metic is that of supplying this in- 
strument with the breath. In- addition to 
pom Se of keeping: up a constant emission oft air paesiat 
and its injurious effect upon the lungs,* it may be 
remakes, ‘that as _ breath is loaded with moisture, and par- 
tially carbonized, it is proportionably unfit for combustion ; 
and the iespcnliliey = supporting a flame with oxygen gas, 
a: this method, is obvious. 
‘* Another = of supplying the blowpipe with air, is that 
of connecting w th it a small pair of double bellows. 
of maxing their valves air tight, the greater part of the air 
drawn into them, escapes at other places than the proper 
aperture. A pair of bellows, of this kind, belonging to an 
artist of this city, which were not considered as less air tight 
than were found to discharge the complement of their 
upper compartment, in in six-sevenths of the time, when the ori- 
fice of the pipe was open, which was requisite when it was 
closed. Hence it appears that six-sevenths of the air ejected 
into the upper compartment, ese at other places'than the 
proper aperture ; and if to this loss were added that sustain- 
ed = the lower compartment, the waste would be much great- 
er. As in operating with these machines, it is necessary 
constantly to move the foot, the operator cannot leave his 
1“ Mtn consequence of this, some artists have abandoned the use of the in- 
