1872.! Electricity. 273 
generated below the obje& to be heated, which, therefore, is not also cooled 
by the passage of unburnt gas and air. The point of greatest heat commences, 
as with a blowpipe, at the point of the blue cones, about } in. or } in. above 
the tubes; and if the flame is protected with a ring of fire-clay, continues 
uniform for some inches above. The great heating power of the hot-blast 
blowpipe is obtained by an arrangement which enables both gas and air to be 
supplied to the jet at an exceedingly high temperature. The jet will fuse 
a strand of 6 or 8 fine platina wires into a bead with a small point of flame, 
and will give a small light with a cylinder of lime. With the gas fully 
turned on, it will melt 3 ozs. of 18-carat gold on pumice-stone. Steel wire 
burns readily, with brilliant scintillations, and wrought-iron wire is readily 
fused. The additional heating power may be used or not at will, and the 
blowpipe can be used either with the mouth or a foot-blower; when used with 
the mouth the head is not confined in one position, as in case of the old form, 
and both hands are at liberty. The extreme power is exerted to the best 
advantage on as smal] objects as possible, and when the gas is turned down to 
a blue cone of about 1 or 1} inches long. The point of this blue cone 
will fuse a few grains of platinum, supported on lime, in five or six 
seconds, if a foot-blower is used. If, however, a smaller quantity is taken— 
say half a grain—it is fused into a bead instantly, either with the mouth ora 
foot-blower. If a platinum wire is used, it should be held with the point 
exactly in front of the point of the blue cone. With care, a bead may be 
fused on the end of a platinum wire almost as thick as ordinary copper bell 
wire. If a very fine wire is used, it will melt almost as quickly as it can be 
passed along the flame: in these experiments the eyes should be protected 
from the blinding glare of light, more especially in fusions on lime. For 
soldering and heating platinum crucibles, the gas should be turned full on, so 
as to produce a large rough flame, the heating power of which is about double 
that of the ordinary blowpipe. The lower burners need never be turned 
on more than is necessary to allow the flame just to reach the top of the coil. 
ELECTRICITY. 
The electric currents obtained by the bending of metals have been examined 
by P. Volpicelli. After relating at length his method of experimenting, he 
summarises the results of his experiments in the following points :—All metals 
when being bent or twisted give rise to the development of an ele@tric current, 
but copper exhibits this phenomenon in the highest degree. Lead, although 
not an elastic metal, also gives rise to the generation of an ele¢tric current, 
thus exhibiting an instance of the conversion of mechanical force into 
electricity ; the electric currents thus produced are not perceptibly due to the 
development of heat due to the action of bending or twisting. When the 
bending is accompanied by the tearing asunder, or, rather, the distending, of 
the two ends of the metallic wire, a current is produced in an opposite direction 
from that obtained by putting the two ends nearer together; by increasing or 
decreasing the velocity of the bending, the intensity of the ele@tric current is 
also increased or decreased. A metallic wire made of various metals soldered 
together produces, other conditions being the same, a less intense current by 
bending than when the wire is made of one and the same metal. 
M. Eugenio de Zuccator has invented a novel method of rapidly copying 
manuscripts or designs, whether produced by hand or photography. An ordi- 
nary letter copying press is used for printing from the design, which is formed 
upon a varnished metal plate. This plate, which is of iron, is either coated 
with a shellac varnish, and the writing or design to be copied then traced 
thereon with a metal point, or it may be coated with gelatine and bichromate, 
and the design produced by means of photography with a transparent positive. 
In any case the lines are formed of bare metal upon a surface of varnish. One 
wire of an electric battery is connected to the bed of the copying press, and the 
other to the upper plate of the instrument, so that when the press is screwed 
down and the top and bottom plates come in contaét, an electric current passes. 
The varnished metal plate, upon which a memorandum has been scratched, or 
VOL. II. (N.S.) 2N 
