Descripiion of a Hydro-pneumatic Blow-pipe. 283 
is filled with tallow, which, melting by the heat, becomes fluid, 
and burns as well as oil, but with a less offensive smell, and when 
cold, being solid, is more conveniently carried than oil. This 
lamp is placed within another vessel marked B, figs. 4, 5, and 8, 
which supports it at a proper height, leaving a space between 
them all round, to receive any tallow which may run over the 
edge of the interior vessel or lamp. 
In using this blow-pipe, the following observations being at- 
tended to, will greatly increase its effect. The long flat cotton 
wick of the lamp will be found to act better than the usual round 
cotton wick; but in either case, the flame which it raises will be 
considerable. The end of the glass pipe a must be just entered 
into the flame, and the current of air will throw out a cone 
of flame from the opposite side. If it is well managed, this 
cone will be distinct and well defined, and extend to a con- 
siderable length. Care must be taken, that the stream of air 
does not strike against any part of the wick, as it would then be 
disturbed, and the cone split into several parts. (A wire bent 
at its end, as shown at fig. 7, is very convenient to smooth the 
passage through the wick :) the jet of air must be delivered some- 
what above the wick ; and as, unless the flame was considera- 
ble, there would not be sufficient for the stream of air to act 
upon, for this reason the wick is opened, as shown in fig. 6, that 
it may expose the largest surface, and produce the greatest 
flame; the stream of air from the pipe should be directed through 
the channel or opening between the wick, so as to produce a 
cone the most perfect and brilliant. On examining this cone of 
flame, it appéars to be formed of two different colours, the part 
nearest to the lamp being of a yellowish white, and that beyond 
of a blue or purple colour. 
The subject which is to be heated, is held in the flame at the 
termination of the yellowish-white flame, where it receives the 
greatest heat, and is not discoloured by the soot which accom- 
panies the white flame. 
Glass tubes are, when applied to this lame, quickly rendered 
pliable, and may be bent or drawn out into threads or points, 
and hermetically sealed; or, by blowing into the other end of 
the tube, it may be expanded into a small glebe, so as to form 
various small articles at the pleasure of the operator. 
In chemistry, mineralogy, and the arts, the blow-pipe is an 
extremely useful instrument, being capable of throwing such a 
powerful heat on a small object, as would be difficult to obtain 
on a larger quantity of the same substance, in the most powerful 
furnaces; and with this advantage, that the process is always un- 
der the inspection of the operator ; whereas he can only con- 
jecture what passes in the centre of a furnace. In 
