^lil^MlCAL DECOMPOSITION FROM ELECTRICITY OF THE TORPEDO. 41 
same time with strong and fresh ones, in the 
difterent cells of a trough, or the different 
troughs of a battery, because, the plates in the 
weaker cells retard the progress of the elec- 
tricity originating in the stronger cells. 
2d. The associating of strong and weak pairs 
of plates should be avoided, as one part is apt 
to act an interposing plate. 
3d. Reversing tin plates, either by accident 
or otherwise, has an injurious effect, by oppo- 
sing tlie current in a manner similar to inter- 
posed plates of platinum. For, in a series of 
four pairs of zinc and platinum plates, in 
dilute sulphuric acid, if one pair be reversed 
it almost neutralizes the power of the whole. 
Other causes affect the passage of the elec- 
trical curient, and there is one especially of 
common occurrence, viz : when the copper is 
precipitated upon the zinc in the cells. 
OBSERVATIONS ON TORPEDO. 
By Dr. Davy. 
Dr. Davy's paper on the Torpedo oculata 
and diversicolor, termed indiscriminately by 
the Maltese, Hnddayla, contains some ex- 
peiimentson the electricity of these species of 
animals, which establish the anticipation of 
Faraday, that by the application of Harris’s 
electrometer to the torpedo, the evolution of 
heat would be observed. In his experiments 
detailed in a former volume of the Transac- 
tions, it was demonstrated that the electricity 
of the torpedo is capable of acting like voltaic 
electricity in effecting chenrical decomposi- 
tions. He enumerates at present all the tests 
or indications of the electricity of the torpedo 
now known, which are, 1st, the philosophi- 
cal effect, as the sensation it imparts is some- 
times calls : 2d, the chemical precipitation of 
iodine, the decomposition of water, &c. : 3d, its 
effect on the thermometer, galvanometer, and 
on steel in the spiral. 'I'hese tests are in point of 
delicacy, in the order in which they are enu- 
merated- Dr. Davy has been unsuccessful in 
his attempts to elicit a spark from the torpedo, 
although it has been said that a spark has 
been obtained fiom the Gymnotns electricus. 
With regard to the seat of the electrical 
power, it appears that when the brain has 
been divided longitudinally, the fish has con- 
tinued to give shocks. When the brain w'as 
completely removed the fish instantly lost this 
power. Humboldt stated that a shock may 
be procured by touching only one surface of 
the fish, but Davy finds that it is necessary 
to touch the opposite surface of the electrical 
organs, or a conductor or conductors connec- 
ted w'ith them, before a shock can be 
received. On some occasions a shock was 
received when only one surface was appar- 
enlly touched, but in that case the discharge 
probably took place through the water, and 
when one surface is touched, the animal 
instinctively makes an effort to bring the 
other surface in contact with the offending 
body, ^ 
There appears, however, to be no connexion 
between the rnuscular and electrical power. 
1 wo views may be taken of the phenomenon. 
It may be considered either, 1st, a form or 
variety of common electricity; or 2d, a 
distinct kind ; or 3d, not a single power, but 
a combination of many powers. The first 
opinion is supported by Dr. Faraday, The 
only objection to it is the interruption of the 
torpedinal electricity by the smallest quantity 
of air, and its want of the power and attrac- 
tion of the air, which affords some foundation 
for the second idea. 
The origin of the electricity of the fish 
may also be urged as an argument for its 
specific nature, but without much plausibi- 
lity, because, we are ignorant of its cause 
and nature. The third opinion may serve as 
a guide for more minute investigation. The 
author suggests that other varieties of electri- 
city may owe their effects to the union of 
several powers, or ethereal fluids, and their 
peculiarities to the predominance, in various 
degrees, of these fluids. Dr. Davy found the 
skin covering the electrical organs, deeper 
coloured and thicker than below, more vas- 
cular, with stronger muscles, and more 
mucus, the under surface having a greater 
supply of cutaneous nerves, and a blood-ves- 
sel enlarged into a little bulb, situated one 
on each side of the porta, below the plexus 
of nerves supplying the pectoral fin, the 
use of which may be to propel the blood into 
the pectoral fin and electrical organ. 
EXPERIMENTS ON THE VELOCITY 
OF ELECTRICITY. 
By Mr. VVheatstone. 
The only remaining paper connected with 
electricity, in this portion of the Transactions, 
consists of an account of experiments by Mr, 
VVheatstone, on the velocity and duration of 
electric light. In 1747 Dr. Watson found 
discharges through a circuit, of four miles in 
extent, two miles through wire and two 
through the ground, to be apparently simul- 
taneous. Mr. Wheatstone repeated a similar 
experiment, substituting for the imperfect 
j udgment of the eye, a revolving mirror. This 
instrument revolved 800 times in a second, 
and during this time the image of a stationary 
point would describe 1600 circles; the elon- 
gation of a spark through half a degree, a 
quantity obviously visible, and equal to one 
inch seen at the distance of 10 feet, would 
therefore indicate that it exists the 1,152,000th 
part of a second. The deviation of half a 
degree between the two extreme sparks, the 
wire being half a mile in length, would indicate 
a velocity of 576,000 miles in a second. This 
estimation is on the supposition that the elec- 
tricity passes from one end of the wire to the 
other: if, however, that two fluids in one 
theory, or the disturbances of equilibrium in 
the other, travel simultaneously from the two 
ends of the wire, the velocity measured will 
be half that in the former case, or 288,000 
miles in a second. The greatest elongation 
of the sparks was 24°, indicating a duration 
of about the 24,000th part of a second. The 
general conclusions wdiich the author draws 
from his experiments are, 1st. The velocity of 
electricity through a copper wire exceeds that 
of light through the planetary space. 2d. 
The disturbance of electric equilibrium, in a 
wire communicating at its extremities with 
two coatings of a charged jar, travels with 
