644 WONDERS OF ART 
escape. The smaller end is bent on one side. For philoso* 
phical or other nice purposes the blow-pipe is provided with 
a bowl or enlargement, in which the vapours of the breatli 
are copdensed and detained, and also with three or four 
small nozzles, with different apertures, to be slipped on the 
smaller extremity. 
The results of the philosophical experiments matte will- 
this instrument are beautiful and truly surprising ; but some 
precautions are required. ■ In describing the blow-pipe in- 
vented by him, Mr. Newman remarks that it has been very 
generally used,- to obtain a high temperature, by the 
COMBUSTION OF OXYGEN AND HYDROGEN GASES. TllS 
mode of rendering this instrument safe, was by rejecting 
all jets but such as were of a very fine bore ; and as any in- 
flammation of gases may be arrested in its passage by an 
aperture sufficiently minute, all danger of the return of the 
flame was thus obviated. A desire, however, to increa.se 
tlie heat, has occasionally led to the use of tubes through 
which the flame could recede, and an explosion has con* 
sequemly happened to ihe apparatus, to the destruction of 
the instrument, and the danger of the e.xperinientalist. 
Doctor Clarke, professor of mineralogy in tlie University 
of Cambridge, obseiwes on this head, that the experiments 
should be made with tubes, whose diameters are, at the 
least, equal to ir'Tjth of an inch, because the heat is thus ren- 
dered incomparably greater ; but, as the danger is also 
greater, it is necessary to devise some expedient, by which) 
making allowance for the probability of an explosion, tlie 
operator may be protected from injury. His contrivance to 
afford him perfect security, whatever explosion may happen, 
consists merely of a screen, made of deal planks, about ii 
inch thick, and reaching about J 2 feet from the floor ot 
the laboratory, so constructed that the one half opens like » 
door, the other half remaining fixed. The blow-pipe is 
placed behind the half that is fixed ; and a small hole is bored 
hrough this half, barely large enough to allow the jet and 
top-cock to pass through. 
The instrument, thus secured, is represented in the piate. 
A i? is the deal screen in two parts j A being made to open, 
and B a fixture, — before the window C. D represents the 
^seous reservoir of the blow-pipe. E, tlie bladder contain- 
ing the gaseous mixture fur compression. F, the hand 
