GALVANISM. 
Having given an account of the effects 
resulting from a single galvanic combina- 
tion, we will next give some account of the 
constructions of that compound apparatus, 
termed Galvanic, or more properly, theVol- 
taic battery. 
The pile of Volta, of which we have al- 
ready given a slight description, is at pre- 
sent so little used, that we shall direct our 
attention more particularly to the trough, 
as being more convenient for experiments 
than the pile, and at the same time less lia- 
ble to be out of order. 
The wood of which the trough is formed, 
should be the oldest and hardest mahogany, 
being less liable to warp than other kinds 
of wood. The sides of the trough must he 
dove-tailed together, and the bottom ought 
to be grooved into the sides, and fitted-in 
with turpentine; perpendicular grooves 
must be made in the sides of the trough, 
for the reception of the plates, correspon- 
dent to which there must be grooves in the 
bottom. When the length of a trough is 
more than two feet, it becomes unweildy ; 
it should not even be that length, when the 
size of the plates would render it too heavy 
to be handed about. The distance between 
'the plates should be about three-eighths of 
an inch ; if they are nearer together, the 
acid employed is too soon exhausted, and 
consequently, the power of the battery less 
lasting. 
The plates should be of copper and zinc. 
Though silver is stronger than copper, it is 
not so in proportion to the price. 
The zinc plates are best cut out of sheets 
of malleable zinc, as being cheaper, less li- 
able to break, and may beused much thinner. 
The copper may be employed so thin as 
six ounces to the square foot. 
The plates of copper being made a little 
larger than the zinc, may be lapped over 
the edges of the latter, by which means 
they fit much closer to the zinc plate, with- 
out the labour of hammering the copper 
plates previously flat. The copper plates 
only require to be soldered to the upper 
edge of the zinc plate, since the other three 
edges are so secured with cement in the 
gVooves as to preclude the necessity of 
soldering. The lapping over of the copper 
is sufficient to keep it close to the zinc 
plate till the plate is fastened in the trough. 
Previously to inserting the plates in the 
trough, the inside must be lined with a ce- 
ment, formed of resin and bees-wax, or what 
is cheaper, of six parts of resin and one of 
lime and oil. The plates, being previously 
wanned, are to be pressed down into the 
grooves before the cement becomes quite 
cold. After the plates have been insert- 
ed, in such order that all the zinc sur- 
faces shall face one way and the copper the 
other, the cement must be more evenly 
adjusted with a hot iron which will reach 
to the bottom of the cells ; the trough being 
laid first on one side and then on the other 
for that purpose. 
When the cementing process is finished, 
and the whole sufficiently cold, the trough 
must be dressed oft' and varnished with 
copal varnish where it can be had ; but in 
lieu of that with common spirit varnish. 
When the varnish is dry it must be polished 
with rotten-stone and water. 
In the above construction it is manifest 
that two of the surfaces are lost by being 
laid and soldered together. About two 
years ago the writer of this article had con- 
ceived the possibility of making use of both 
the surfaces of the copper and zinc plates 
at the same time. Accordingly he cement- 
ed into a trough, in the groove made for 
the plates of metal, plates of glass. The 
metal plates were formed by soldering to- 
gether a plate of each, of copper and zinc, 
and then bending them till the plates be- 
came parallel to each other, leaving a space 
between the two surfaces a little wider 
than the thickness of the glass plates. 
The cells between the glass plates being 
filled with the proper liquid, each of the 
above compound plates were made to be- 
stride one of the glass plates, in such order 
that a zinc and copper plate of two differ- 
ent compound plates, in succession to each 
other, may occupy each of the cells. All 
the surfaces are by this contrivance exposed 
to the action of the liquid, and might be 
considered double the power of a common 
trough, having the same number of plates. 
Little or no advantage was gained by 
this method. Though there are two sur- 
faces of each metal in each of the cells, 
it will be evident, flora several minor ex- 
periments already given, that two of the 
surfaces are so completely disconnected as 
to produce little or no effect. One of the 
zinc surfaces in this trough is facing the 
glass on one side the cell, and one of the 
copper surfaces is similarly situated on the 
other side. 
The trough, therefore, which is repre- 
sented in figure 1, and which has been par- 
ticularly described, is, for general use, the 
most convenient, and in other respects, the 
best battery yet introduced. 
S 2 
