tween the’ points of the wires in the water was one 
inch and three quarters. This compound discharger 
was applied, so that the external ends of .its wire were 
in contact with the two extreme plates of a pile of 36 
half-crowns, with the correspondent pieces of zinc and 
eboard.. A fine stream of minute bubbles imme- 
diately began to flow from the point of the lower wire 
in the tube, which communicated oth the silver, en 
the opposite point of the upper wire became tarnished, 
first ot yo and then black. On reversing the 
tube, the gas came from the other point, which was 
now lowest, while the upper, in its turn, became tar- 
nished and black.”—‘ The product of gas, during two 
hours and a half, was two-thirtieths of a cubic inch. 
Tt was then mixed with an equal quantity of common 
air, and exploded by the application of a lighted waxed 
‘the body They observed, that the same process of the decom- 
pile. position of water is carried on in the body of the pile, 
as between the two ends of the wire in the interrupted 
circuit; the side of the zinc next to the fluid being co- 
vered with oxide in two or three days, and the appara- 
tus then ceasing to act. Mr Nicholson found, that, by 
using metallic plates of considerably more extensive 
surface, no greater effect was produced in the decom- 
ition of water, or in the violence of the shock; so 
that he concludes, “ the repetition of the series is of 
more consequence to this action than the enlargement 
of the surface.” It was now clearly ascertained, that 
the electricity of the silver or minus end was negative, 
that of the zinc or plus end positive. Although it ap- 
peared evident that there had been a decomposition of 
water effected by the copper wire, yet Mr Nicholson 
determined to render the operation more decisive, by 
atin: employing a metal which was not oxidable. Platina 
tes pro- was therefore substituted for the copper, and now gas 
both was disengaged from both sides, and neither of the 
bya eel! wires were tarnished. In a subsequent experiment, 
AT! the wires were so managed, that fhe gases extricated 
XIII. from each side were kept distinct, and it was found 
that they consisted, the one of oxygen, and the other 
of hydrogen, and that in the proportion necessary to 
produce water. In some of these experiments the spark 
was visible (Nicholson’s-Journal, 4to, iv. 179.) Our 
readers will at once perceive the important views 
that were disclosed by the experiments related in this 
Benet, in connexion with those performed by Mr 
ruickshanks of Woolwich, of which we shall next 
give an account. They must be regarded as leading 
i y to the wonderful discoveries that have been 
made by means of the galvanic apparatus, as well as 
the theoretical deductions to hich it has given rise, 
and which have produced almost a complete revolution 
in our ideas of the action of bodies upon each other. 
Mr Cruickshanks confirmed the observations of Messrs 
Nicholson and Carlisle, respecting the actual appear- 
ance of sparks and the decomposition of water. This 
last bigs he varied in different ways. By employ- 
ing the interrupted circuit with silver wires, and pass- 
ing the influence through water tinged with litmus, he 
found, that the wire connected with the zine end of 
the pile communicated a red tinge to the fluid conti- 
guous to it ; and afterwards, by employing water tinged 
with Brazil wood, he found that the wire connected 
with the silver end of the pile produced a deeper shade 
of colour in the surrounding fluid. Hence it appeared, 
that an acid was formed in the former, and an alkali 
in the latter case. The galvanic influence was 
through the interrupted circuit, in which the tube was 
nk’, 
8 eX- 
r 
mt: 
GALVANISM. 
83 
filled with the solution of acetate of lead, when it was History. 
observed that the lead was separated in the metallic ~~~ 
state, and deposited at the end of the silver wire, or (°°) trom 
the wire connected with the silver end of the pile, in metallic so- 
the form of fine needles. Experiments were afterwards lutions. 
made upon the solutions of sulphate of copper and ni- 
trate of silver: in this last case, he observes, “ the me- 
tal shot into fine needles, like crystals articulated or’ 
jointed to each other, as in the Arbor Diane.” He 
also succeeded in decomposing some of the neutral 
salts. See Nicholson’s Journal, 4to, iv. 187. 
In a second memoir, Mr Cruickshanks paid more 
icular attention to the nature of the gases emitted 
in the interrupted circuit—to the effects of different 
kinds of wires—and to the influence of the fluid me- 
dium upon the decomposition of the water.. Some of 
his most important conclusions are, that from the wire iat bodies 
connected with the silver or copper end of the pile, gen ical. 
whatever be its composition, if it terminate in water, ways emit- 
the gas emitted is chiefly hydrogen ; if it terminate in ted from 
a metallic solution, the metal is reduced, and is deposi- ron wire, 
ted at the end of the wire. When the wire connected 0" ‘2° _ 
with the zine end is formed of a perfect metal, nearly gen, or 1 
pure oxygen is disengaged ; when of an oxidable me- wire oxida- 
tal, it is partly oxidated and partly dissolved, and ioe ted. 
a small quantity of oxygen is liberated. When fluids piuidswith- 
contain no oxygen, they appear to be incapable of out oxygen 
transmitting the galvanic influence; while, on the con- Will not act - 
trary, it would seem that it may be transmitted by 
every one which contains this element, (Nicholson’s 
Journal, 4to, iv. 258.) These views of Mr Cruick- 
shanks respecting the action of the pile were confirm- 
ed by some experiments that were performed, about 
the same time, by Colonel Haldane. He found that Haldane’s 
the apparatus ceased to act when it was immersed in experi- 
water, or if it was placed in the vacuum of an air- ™*"* 
pump. He found, on the contrary, that it acted more Pile will 
powerfully in oxygen gas, than when confined in an notactwith- 
ual bulk of atmospheric air, while azote had the same °U* °*Y8e% 
ect asa vacuum. ‘These circumstances led him to 
conceive that its action depended essentially upon the 
combination of oxygen, which it derives from the 
atmosphere. See Nicholson’s Journal, 4to. iv. 242, 
313. i 
In the early part of his experiments, Mr Cruickshanks Trough ap- 
invented a new manner of disposing the apparatus, paratus. 
which has proved scarcely less important to the inte- PLATE 
rests of science, than its original discovery by Volta. We vn ee a. 
allude to the method of placing the metals horizontally °* 
in a frame or trough, with proper intervals for contain- 
ing the fluid which is intended to act upon them. 
The power of the pile in decomposing chemical sub- 
stances being now established, by the experiments of 
Nicholson and Cruickshanks, a new field of investiga- 
tion was opened, which was ardently entered upon, b 
some of the most distinguished among the English che- 
mists. Dr Henry decomposed the sulphuric and nitric syenry’s ex. 
acids, and ammonia, and he reduced the oxymuriatic periments. 
to the state of muriatic acid; but as gases do not con- Decompo- 
duct the galvanic influence, its decomposing power ses acidsand 
could not be applied to this last body. See Nicholson’s ammonia. 
Journal, 4to. iv. 223. 245. 
Sir H. Davy commenced his discoveries in galvanism Davy’s ex- 
at an early period of the investigation. He proposed, periments. 
as a subject of experimental research, whether the ends pjcen 
of the wire, in the interrupted circuit, would discharge the gases 
the two gases, if they were made-to terminate in diffe- from two 
rent portions of water. The ends of the wires were Portions of 
therefore placed in separate glasses, while the glasses “““* 
5 
Concludes 
