316 Hare’s Eudiometers and Calorimotor. 
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eter. The whole is cemented into the perforation drilled 
in the tube, so as that the smallest part may extend across 
the bore. The wire should then be cut off at about one 
third of an inch from the tube, so as to stand out from it 
on each side about that distance. If these protruding wires 
be severally placed in the forceps of a calorimotor and the 
plates subjected to an acid, the small part of the wire within 
the tube is vividly ignited, and any gas in contact with it 
must explode. ‘The interior wire is best made of plaiina, 
and may in that case be screwed into two larger pieces of 
a baser metal ; or a baser metal may be fastened on it, by 
drawing through a wire plate, and the platina duly denuded 
by a file where it crosses the bore. 
The calorimotor which I have used for this purpose, con- 
sists of eleven plates of copper, and a like number of zinc, 
placed alternately within one-fourth of an inch of each 
ether ; those of the same kind of metal being all associated 
by means of a metallic stratum of tin cast over them. The 
two heterogeneous galvanic surfaces thus formed, have each 
soldered to them a wire in a vertical position, and slit, so 
as to present a fork or snake’s mouth. The wires are just 
so far apart as to admit the gas measurer between them, so 
that the wires of the latter may easily be pressed into the 
snake mouths. It is better that the wires of the gas meas- 
urer should be flattened in such manner as to present a 
larger surface for contact. There must also be an oblong 
square box or hollow parallelopipedon of such a width as 
just to admit the calorimotor, and more than double its 
length and depth. The calorimotor is placed within this 
box, at one end of it, about an inch below the brim. Dilut- 
ed acid is poured in so as to occupy the lower half of the 
vessel, until it nearly reaches the plates. A plunger, con- 
sisting of a water tight box, or solid block of wood, is then 
made to occupy the other side of the little cistern. The 
depression of this causes the rise of the acid among the 
plates in the calorimotor, and consequently the ignition of 
a wire forming a communication between the surfaces. 
This apparatus may be constructed in the circular form, 
by so placing two concentric coils, or several concentric 
hollow cylinders of copper and zinc, alternately within the 
upper half of a glass jar as to admit of a plunger in the mid- 
dle, which in this case may be of an apothecaries stopper 
