potash (which had previously been exposed to the atmosphere, so as to
render it a conductor of the Galvanic fluid,) upon an insulated plate of
platina, connected with the negative[20] end of a battery, of the power
of two hundred and fifty plates, six inches by four, in a state of
intense activity.—A wire communicating with the positive end, was
brought in contact with the upper surface of the alkali. The whole
apparatus was in the open air. Under these circumstances a vivid action
was soon perceived.—The potash began to fuse at both points where the
fluid acted upon it.—There was a violent effervescence at the upper
surface:—at the lower or negative surface there was no liberation of
elastic fluid, but there appeared small metallic globules, very much
resembling quick-silver. Some of these globules burned with an explosion
and a bright flame, as soon as they were formed, while others remained
which were merely tarnished; and finally a white film was formed over
their surfaces, which was afterwards found to be pure potash.
Soda was acted upon in the same manner as potash, and exhibited the same
results; but its decomposition required a stronger action of the
battery, or it was necessary that the soda should be in smaller pieces
than the potash.
The metallic globules produced from the potash remained fluids in the
open air, at the time of their production; but those from soda, though
fluid at the time of their formation, upon cooling, became solid, having
much the lustre of silver. The alkalies could be made to produce
metallic results in vacuo.
Since Mr. Davy’s first experiments on this subject, several others have
been made, much in the same manner, upon the earths. Messrs. Pontin and
Berzelius, two Swedish chemists, have succeeded in obtaining metallic
amalgams from lime, magnesia, strontites and barytes; but they could
produce no such effect on alumine and silex. Mr. Davy however effected
this, by a battery of 36000 square inches.—He also improved upon their
other discoveries. He, by distillation, drove off the mercury from the
amalgamated metals which they obtained from the earths, and procured a
pure metal.
Ammonia was also found to contain a metal. This discovery inclines one
to believe, that the air we breathe contains metal in a gaseous state,
as azote, which is a component part of ammonia, forms a large portion of
our atmosphere.
When compounds, soluble in water, were put into water contained in agate
cups, and subjected to the action of Galvanism, their decomposition was
rapid.—A solution of the sulphate of potash, being put into two cups and
Galvanised by fifty pair of plates, for four hours, the acid was found
by itself in the cup connected with the positive end of the battery, and
the alkaline basis in the cup communicating with the negative end.
Similar phenomena took place in solutions of sulphate of soda, nitrate
of potash, nitrate of barytes, phosphate of soda, sulphate, succinates,
oxalate and benzoate of ammonia; also with alum. When muriatic salts
were used, they afforded oxymuriatic acid. When metallic solutions were
employed, metallic crystals and an oxyd were deposited on the negative
wire, and a great excess of acid was found in the positive cup.—Strong
solutions afforded signs of decomposition quicker than weaker ones.
We could enumerate a variety of similar experiments, but the limits of
our work forbid it.
CHAP. VIII.
_Experiments which may be performed without the assistance of the
Battery._
_To shew the Galvanic light._
Place a piece of zinc upon your tongue, and a piece of silver between
your cheek and upper jaw; then move your tongue so as to bring the two
metals in contact with each other, and you will perceive a very curious
sensation upon your tongue, accompanied by a cool sub-acid taste,[21]
and at the same time you will see a _flash of light_, whether your eyes
be open or closed. The sub-acid taste resembles, in a degree, that
produced by electricity.[22]
_To affect the Taste by means of Water._
Place a tin or pewter bason filled with clean water upon a silver mug:
with both your hands, which must previously be wet with a solution of
salt in water, grasp the silver vessel, and put your tongue into the
water, taking care not to touch the tin or pewter vessel with any part
of your body; you will now perceive an acid taste; which will be more
sensible, if you withdraw your hands from the silver vessel while your
tongue remains in the water, and then replace them.
_To prove that Earth-Worms have a nervous system._
Place an earth-worm upon a plate of zinc, resting on a larger plate of
silver.—The animal, as soon as it approaches the silver, seems to be
repulsed by a painful sensation, and at last becomes fatigued by its
repeated and fruitless exertions to make its escape, which nothing
apparently prevents.
This evidently proves that the animal is provided with a nervous system,
as experiments have proved that Galvanic irritation is excited only in
the nerves.
CHAP. IX.
_Some common Effects which are supposed to be occasioned by Galvanism._
We have already remarked, that a sub-acid taste is perceptible when two
different metals are applied to the tongue and fauces: it has also been
found that Galvanism affects the taste, when two different _fluids_ and
a single metal are in contact with the tongue. Upon this principle a
variety of known facts have been accounted for.—For example—It has long
been observed that beer, cyder, &c. when drunk from a tin or silver
vessel, were more palatable than when received from a vessel of glass,
or any other substance not metallic. The supposed explanation of this,
is as follows.—When the outer extremity of the vessel is applied to the
under lip, rendered moist by the saliva, and the tongue is extended so
as to be in contact with the liquid contained in the vessel, a Galvanic
arc is formed, which produces the brisk and lively taste.
It has been supposed, by persons fond of this theory, that snuff, when
taken from a metallic box, excites a more agreeable sensation than when
taken from a box of tortoise shell, or leather.
The fact that a silver spoon becomes discoloured by being used for
eating eggs, is familiar to every one. This, also, is attributed to the
Galvanic action. By experiment, sulphur has been discovered in both the
albumen and yolk of an egg.—The Galvanic combination is between the
sulphur of the egg, the silver spoon, and the saliva; for no tarnish is
produced on the spoon when it is immersed in either the albumen or yolk;
and that part of the spoon which enters the mouth is most discoloured.
In every Galvanic experiment, water is decomposed into its constituent
parts, hydrogen and oxygen gases. These things being premised, the fact
is easily accounted for.—The hydrogen, which before the operation is
nascent in the water, (which holds the sulphur in solution) now readily
unites with the sulphur, and forms sulphurated hydrogen gas, which
produces the tarnish on the silver.[23]
We shall mention a few other common appearances, and leave the solution
to the ingenuity of the reader.
When copper sheathing is fastened on a ship with iron nails, the nails,
and particularly the copper, are found to be corroded about the places
of contact.
Works of metal, the parts of which are joined by a solder of a different
metal, are observed to tarnish about the places where the different
metals meet. A seam which has been soldered so accurately that it cannot
be perceived by the eye, may be discovered by passing the tongue over
it.
CHAP. X.
_The Effects of Galvanism on Vegetables._
This part of Galvanism has been particularly attended to by Humboldt, a
German. He first observed the irritability of the vegetable fibre.
Remarking the great similarity of appearance between the substance of
mushrooms and the muscular fibre, he wished to ascertain whether they
possessed a similar power of contraction. He accordingly made a
considerable number of experiments, from which he concluded that the
different kinds of mushrooms, which in becoming putrid emit an animal
insipid cadaverous smell, are as perfect conductors in the Galvanic
chain as the organs of animals. His experiments likewise proved that
they possessed irritability.
Mr. Humboldt afterwards directed his inquiries to the _manner_ in which
Galvanism acted upon the irritable fibre, which, as we have already
mentioned, he first observed. These experiments, however, were
unsuccessful. We shall not therefore relate them.
The effects of Galvanism on vegetation are supposed to be deleterious,
as will appear from the following extract from the “Monthly Magazine.”
“It often happens, that some of the limbs of fruit trees, trained
against a wall, are blighted and die; while others remain in a healthy
and flourishing state. This evil is, by gardeners, generally attributed
to the effects of lightning. But, if this were the case, would not the
violent action of the electric fluid produce a laceration of the branch
and stalk of the tree? No such effect is to be perceived. It therefore
appears to me, that we must seek some other cause for this evil, and I
flatter myself that I have discovered the real one.
A few years since, when Galvanism was first introduced to public notice,
I constructed a pile, consisting of about one hundred plates of copper
and as many of zinc, each about two inches square. Among other
experiments, I applied it to the branch of a tender plant, (a species of
the ficoides.) Having left it for about an hour, on my return I found
the branch withered, and hanging close to the stalk. It immediately
occurred to me, that Galvanism might be the cause of the above mentioned
defect in wall fruit trees, occasioned by the oxydation of the nails, by
which they are oftentimes fastened (for I conceive Galvanism to be
produced, in a greater or less degree, by every metal passing into a
state of oxydation.) Recollecting that the limb of a cherry tree in my
garden had, nearly a year before, been fastened to the wall with an iron
cramp, I instantly examined it, and found it dead; though, when
fastened, it was a flourishing, healthy limb, at least an inch in
diameter, and nine feet in length.
I have since examined several peach and nectarine trees; and wherever I
discovered a limb dead, I invariably found that one or more of the nails
which fastened it were in _contact with the bark_. A limb of a peach
tree puzzled me for some time. It was dead, but I could not perceive
that any of the nails were in contact with it, (the scraps of cloth
being left pretty long.) After a narrow search, however, I found the
mud, of which the wall was built, considerably stained with rust,
immediately under the branch: and on digging into the wall with my
knife, I brought the hidden mischief to light.—It was part of a very
large spike nail, and which lay about an inch below the surface.
On mentioning some of those circumstances to a friend, he observed, that
about a year before, he had fastened some currant trees to a wall, with
iron hooks. On examination, almost every limb so fastened, _was dead_.
The effect of the Galvanism in these cases will probably be found to be
greater in rainy seasons, as the oxydation then goes on more rapidly
than it does at other times.
Hence it appears that, in training fruit trees, wooden pegs or cramps,
should be used instead of iron; or else, that care should be taken that
the iron do not touch or come near to a limb.
CHAP. XI.
_Of medical Galvanism._
Galvanism, like electricity, has been applied to the human body, for the
purpose of removing complaints, and apparently with equal success.
The ingenious Galvani, immediately after his discovery of Galvanism, (or
as he called it, _animal electricity_,) attempted to explain the causes
of several diseases by it. Thus in a complaint where there was a total
loss of contractile power, as the paralysis, he ascribed the cause to
the interposition of a non-conducting substance, which prevented the
passage of the Galvanic fluid from the nerve to the muscle, and from the
muscle to the nerve. “If artificial electricity (says he,) be conveyed
to the head, the nerves or spinal marrow, by means of the conductor of
the Leyden phial, paralysis, apoplexy, and even death, will be induced,
according as the phial is charged with a greater or less quantity of the
electric fluid.—If such effects result from _common_ electricity, may it
not be presumed that a sudden afflux of _animal_ electricity towards the
brain, may be productive of the most fatal consequences.”
But omitting, as wholly conjectural and unsatisfactory, all _theories_
relating to the effect which Galvanism has upon the animal œconomy, we
shall proceed to relate known facts, and the method of applying
Galvanism for the relief of certain morbid affections of the human body.
The general mode of operating with Galvanism, is to apply small portions
of it at first, and gradually to increase the shock, as circumstances
may dictate. It has been customary to remove the cuticle (by means of a
blister or otherwise,) from the parts of the body to which the wires,
communicating with the two extremities of the battery, are to be
applied. This method, which was adopted because the cuticle is a very
bad conductor, gave excruciating pain to the patient. Mr. Wilkinson has
found it unnecessary, as by moistening the parts, and applying pieces of
gold leaf or Dutch-metal, he has succeeded in producing the desired
effect. During an operation, one of the conducting wires should be kept
in contact with one of the metallic leaves, while the other conductor is
to be removed, immediately after it has been brought in contact with the
other metallic-leaf—and then replaced and removed successively.
The negative wire of a battery is the most powerful, and it is necessary
in some cases to attend to this fact.
In a short time after Galvanism has been applied to a part of the body,
a redness becomes perceptible about the part; and if the application be
continued too long, vesications and ulcerations will be produced. These
symptoms are a little troublesome at first, but do not require any
particular treatment for their cure.
Galvanism should be applied twice in twenty four hours, otherwise it is
supposed the intervals would be so long, as to prevent any good effects
which might arise from it.
We shall now enumerate some disorders in which Galvanism has proved
beneficial. In _paralytic affections_ it has afforded considerable
relief.—Two instances of _mental derangement_ are recorded by professor
Aldini, nephew to Galvani, in which its effects were truly
surprising.—One of them afforded an instance of a gradual diminution of
the mental energies, which ultimately sunk into stupidity. The other was
of an opposite nature:—the system was in a state of violent excitement,
and the patient raving and unmanageable.
In _rheumatism_, _spasmodic affections_, and _deafness_, where it does
not arise from a natural defect in the organ, Galvanism has been applied
generally with advantage. But the most astonishing effects of this
wonderful principle have been displayed in cases of _suspended
animation_. Mr. Humboldt made the first experiments relative to this
part of our subject, on apparently dead linnets. He put a piece of zinc
into the bill, and thrust a sharp piece of silver into the bird, near
the other extremity of the body—he then formed a communication between
the two, by an iron wire. “What (exclaims he) was my surprise, when I
perceived, the moment the contact took place, the linnet open its eyes,
stand erect on its feet, and flutter its wings; it again breathed during
six or eight minutes, and then expired tranquilly.”
Galvanism is now applied to persons apparently dead, from drowning,
hanging, or exposure to noxious gases. In such cases, the body should be
divested of its clothing, and placed in a warm bed nearly approaching
the natural temperature, and at the same time slight Galvanic shocks
should be passed through the body, in such a direction as to affect the
heart.—Thus by combining this, with the usual means, the most
advantageous consequences may be expected. It may be laid down as a
principle, that, in all cases where animation is suspended, and the
principle of irritability not destroyed, the stimulus of Galvanism and
electricity, if prudently employed, may rouse the dormant energies of
vitality, and restore the system to its natural state of activity.
CHAP. XII.
_The Identity of Galvanism with Electricity considered._
It has been supposed by many, that the phenomena of Galvanism and
electricity depend upon the _same_ cause. Others, however, controvert
this opinion, and affirm that Galvanism is a fluid _sui generis_. That
there is a great similarity between some of the phenomena of Galvanism
and those of the electric fluid, is evident; but this analogy cannot be
traced in every instance.
It is not our province to enter into this controversy; we shall only
relate a few facts upon which it is founded, and leave the speculative
reader to draw from them his own conclusions.
_Facts which seem to indicate that Galvanism and Electricity are the
same Fluid._
Both Galvanism and electricity exhibit light, in their passage from one
conductor to another, through an intervening space of air.
Both affect an electrometer.
The deflagration of metals may be produced by either.
Electricity, as well as Galvanism, produces muscular contractions in
animals, a short time after death.
_Facts in which Galvanism and Electricity differ from each other._
Some _good_ conductors of electricity are not good conductors of
Galvanism; as was shewn by Dr. Fowler.
The manner of exciting Galvanism is different from that of exciting
electricity;—the former being collected most copiously from
_conductors_, and the latter from _non-conductors_.
The electric fluid affects the sense of smelling—but no smell has ever
been observed from Galvanism.
The electric shock operates on the body by a sudden and percussive
effect—while the one which follows the Galvanic process seems to arise
from a constant current, attended by a jarring and tremulous sensation.
In the decomposition of water by Galvanism, hydrogen gas is formed at
one of the wires, and oxygen at the other. In that by electricity, both
gases arise from the same wire.
FINIS.
INDEX
TO
THE EPITOME OF
ELECTRICITY.
A
_Æpinus’s_ theory of electricity, 115
_Amalgam_, directions for making the best kind of, 126
_Apparatus_, electrical, directions for using the, 68
_Attraction_, electrical, 21
_Aurora Borealis_, how to imitate the, 79
B
_Balloons_, inflammable air, 77
_Battery_ electrical, and experiments with it, 28
_Bells_, electrified, 76
_Black lead_, useful for points to lightning rods, 51
_Bladder_, electrified, 93
_Bolognian stone_, artificial, to make, 127
_Bottle director_ described, 65
C
_Candle_, to light a, 91
_Cannon_, the electrical, 96
_Cards_ pierced by electricity, 90
_Cavallo_, general laws deduced by him from experiments made with
electrical kites, 46
_Cement_, how to make, 125
_Charcoal_ useful at the lower extremity of lightning rods, 53
_Chemical_ theory of electricity, 111
_Clay_ swollen by the electrical shock, 90
_Colours_ changed by the electrical shock, 87
—— experiments on, 87, 88
_Communication_, electrifying by, 15
_Conductors_, of, 6
—— luminous, 82
_Constellations_, to represent the, 101
_Cotton_, electrified, 92
_Cylinders_, of, 9
—— composition for lining, 125
—— plates may be substituted for, 14
D
_Dance_, electrical, 75
_Decomposition_ of water by electricity, 103
_Director, bottle_, description of, 65
—— use of, 67
_Discharging_ electrometer, description and use of, 67
—— rod, luminous, 103
_Du Fay’s_ theory of electricity, 109
E
_Electric attraction and repulsion_, 21
—— —— —— —— exemplified, 22, 24
—— battery and experiments with it, 28
—— eel, an account of the, 56
—— fly, described, 18
—— light, experiments with, 79
—— spark, 16
_Electric_ spider, 25
_——s_, and phenomena produced by them, 2, 3, 6, 8
—— experiments with charged, 86
_Electrical_ machine described, 9, 13
_Electricity_, the identity of with lightning, 40
—— how it may be applied to the best advantage, 65
—— animal, 55
—— apparatus necessary for, 64
—— atmospheric, danger of making experiments with, 42, 44
—— medical, 63
—— positive and negative, 2
—— various theories of, 108
_Electrometer_ described, 36, 64
—— instructions for using, 37
_Electrophorus_ described, 33
—— experiments with the, 34
_Excited_, what is intended by, 1
_Experiments_, practical rules for making, to the best advantage, 68
—— promiscuous, 94
_Explosion_, the lateral, 101
F
_Figures_ made upon glass &c. by means of electricity, 97
_Fountain_, the electrified, 104
_Fractured jar_, how repaired, 70
_Franklin, Dr. his experiment_ with a kite, 40
—— —— —— —— for illustrating his theory of thunder storms, 78
—— his theory of electricity, 116
_Friction_, electric, 65
G
_Gibbes Dr._ his theory of electricity, 113
_Glass_, metals forced into, by an electric explosion, 30
_Gun-powder_ fired by an electric explosion, 30
I
_Jack_, the electrical, 94
_Jar_, electrical, fractured, how repaired, 70
K
_Kite_, Dr. Franklin’s experiment with a, 40
—— _electrical_, structure and use of the, 41
—— —— Cavallo’s directions for using the, 43
L
_Lane’s_ discharging electrometer, 67
_Leyden phial_ described, 26
—— —— experiments with the, 27
—— vacuum, 81
_Light, electric_, experiment with, 79
—— —— flashing between two metallic plates, 83
_Lightning_, the identity of with electricity, 40
—— _rods_, the structure and use of, 48, 54
—— —— improved by professor Patterson, 51
_Luminous_ conductor, 82
—— to render various substances, 84
—— shower, 102
M
_Machine_, electrical, described, 9
_Magic_ picture, 86
_Magnetic needle_, effect of electricity on the, 31
_Medical_ electricity, 63
_Metallic oxyds_ revivified, 31
_Metals_ forced into glass by an electric explosion, 30
N
_Natural state_, meaning of, 2
_Nollet’s Abbè_, theory of electricity, 110
_Non-electrics_, 2, 7
O
_Oxyds_, metallic, revivified, 31
P
_Paint_, for electrical purposes, preparation of, 126
_Paper_ stained by an electric explosion, 31
_Picture_, magic, 86
_Pointed bodies_, their influence on electricity, 17, 92
—— —— phenomena attending, 17
—— —— conclusions respecting, 21
_Powder, gun_, fired by electricity, 30
_Prime-conductor_, 12
R
_Repulsion_, electrical, 21
_Richman_, Professor, killed by atmospheric electricity, while making
experiments with it, 42
_Rubber_, defined, 2
—— described, and directions respecting it, 10
S
_Shower_, luminous, 102
_Snake_, electrical, 102
_Spark_, electric, 16
—— —— applied for curing deafness &c., 66
—— —— to render the, visible in water, 84
_Stream_ —— useful in curing diseases of the eye, 67
_Syphon_, the capillary, electrified, 100
T
_Terms_, explanation of, 1
_Thermometer_, effect of electricity on the, 32
_Thunder-house_, experiments with the, 54
_Torpedo_, an account of the, 58
—— artificial, to make, 60
_Tube_, spiral, 83
—— the self-charging, 95
V
_Vacuum_, what is meant by the term, 79
—— Leyden, 81
_Vegetables_, effect of electricity on, 61
_Velocity_ of electricity, 15, 29
W
_Water_ decomposed by electricity, 103
_Wheels_, multiplying, may be added, with advantage, to an electrical
machine, 12
—— self-moving, described, 74
_Wilson’s_ theory of electricity, 109
_Wine_, spirit of, fired by electricity, 89
INDEX
TO
THE EPITOME OF
GALVANISM.
A
_Animals_, cold blooded, best for Galvanic experiments, 131
_Arc_, animal, and excitatory, 132
B
_Berzelius_, his experiments, 147
C
_Conclusions_, 139, 143
_Conductors_, Galvanic, 133
_Cruickshank’s, Mr._ experiments, 140
D
_Davy Mr._ his experiments, 146
_Diseases_ in which Galvanism has afforded relief, 156
E
_Effects_, common, supposed to be occasioned by Galvanism, 150
F
_Frogs_, Galvanic experiments upon, 138
—— —— —— —— conclusions drawn from, 139
G
_Galvanism_, a short account of, 129
—— medical, 154
—— identity of, with electricity, considered, 157
L
_Light_, Galvanic, to exhibit, 148
M
_Metals_, most suitable for Galvanic experiments, 132
—— on the deflagration of, by the Galvanic pile, 143
P
_Pile, Galvanic_, description of the, 134
—— —— experiments with the, 140, 143
—— —— its two extremities in opposite states, 146
_Pontin Mr._ his experiments, 147
T
_Trough, Galvanic_, description of, 136
—— —— experiments with the, 146
V
_Vegetables_, effects of Galvanism on, 152
W