136 40 . Black. Brownish purple 238. Mr. Singer was of opinion that the charges here given by Mr. Cuthbertson were rather high, and attended with considerable risk of fracture to the jars: he repeated the experiments with shorter lengths of wire, and of less diameter; and with more moderate charges obtained the following results :A. B.

Gold wire Silver wire Platina wire Copper wire Iron wire Tin wire

18

18

13

T60

12

T 12

11

C.

Purple and brown.
Gray, brown, and green.
Gray and light brown.
Green, yellow, and brown.
Light brown.

Yellow and gray. Zinc wire T 17 Dark brown. Lead wire. T 10 Brown and blue gray. Brass wire. 12 Purple and brown. 239. In the above experiments Mr. Singer did not use the receiver; the wires, which were five inches in length, were stretched parallel to the surface of a sheet of paper, and distant from it about one-eighth of an inch. Brass wire is sometimes decomposed by the electrical charge, in which case its component parts, copper and zinc, are separated from each other, and appear in their distinct metallic colors when the explosion is made over a piece of glass. Indeed the figures of all the oxides are most beautiful when impressed on glass, although their colors are certainly less permanent.

240. This most amazing power of the electric matter is not only adequate to the oxidation of metallic substances, but is yet more remarkable in restoring oxides, already formed, to their metallic, or original state, for which purpose a very simple process will be found sufficient.

241. Into a small glass tube introduce a little of the oxide of tin; let it cover about half an inch of the lower internal surface. Place the tube thus prepared on the table of Henley's discharger, and introduce the pointed wires at each end, that the oxide may form part of the circuit. Pass now several strong charges in succession through the tube, taking care to replace the oxide in its proper situation, should it be dispersed. If the charges are strong, the tube will soon become stained with the tin revived from the oxide.

242. In the same way other metallic oxides may be revived; but if vermilion be employed,

which consists of sulphur and mercury, the mercury will be separated with such ease as that the charge of a moderately sized jar will be found quite sufficient.

DECOMPOSITION OF WATER BY ELECTRICITY.

243. The decomposition of water by electricity was first effected by Van Troostwyk and Deiman, assisted by Mr. Cuthbertson; this they effected by means of a complicated apparatus, and a very tedious process. Their method of procedure was improved on by Dr. Pearson, and after him by Mr. Cuthbertson: but the most simple form of an apparatus for this purpose is that of Dr. Wollaston. This apparatus is thus constructed :-Two finely pointed wires of gold or platina are inserted into capillary tubes; each wire is thrust into the tube till it nearly reaches until it adheres to the wire and covers its point. the end of it, and the glass is softened by heat The glass is then carefully ground away, till the point of the wire can be seen by the help of a magnifying glass. One of these wires is made to tive conductor of the machine, and the other communicate with the ground, or with the negawith an insulated ball placed near the positive conductor, the two points are placed near each other in a vessel of water; when a current of sparks is discharged through the wires, a series of minute bubbles of gas will rise from the points of the gold wires, and, when collected in an inverted receiver, will explode on the application of a lighted taper. Dr. Wollaston found by experiment, that a point of an inch in diameter, decomposed the water when the spark which passed from the conductor to the insulated ball was of an inch in length; and that a point

of an inch in diameter, produced the same effect when the sparks were only of an inch in length. Hence the rapidity of the decomposition was in proportion to the limited size of the point of the wire.

244. Of the results obtained in some experiments made with this apparatus, Dr. Wollaston gives the following account. By transmitting a current of sparks by means of two gold points over the surface of a card a little moistened, and tinged with litmus, and placed between the points, a redness was perceived about the positive wire after a few turns of the machine. When the negative wire was placed upon the red spot it was quickly restored to its former color. Hence he infers that the effect of an acid is produced at the positive wire; and that this effect is counteracted by reversing its electricity.

245. Dr. Wollaston next coated two wires with sealing-wax, so that their ends only were exposed: these he inserted into a solution of copper, and found that, on transmitting a current of sparks between them, the negative wire was coated with copper: the electricity of the wire being reversed, the copper quickly disappeared

246. When it is wished to decompose oils, alcohol, ether, &c., a much more simple, and less expensive apparatus will be found to answer every purpose. This apparatus, which is represented by fig. 8, consists of a glass tube having a platina wire projecting from the top inwards and reaching nearly to the lower end. The lower

extremity is open, and is placed in a metallic dish nearly filled with the fluid which is to be decomposed. The cylinder must be filled with the fluid as receivers are filled with water in the pneumatic trough. When charges are successively sent through the wire, the fluid will be gradually decomposed, and the gaseous product rising to the upper part of the cylinder will displace the liquid. In all experiments of this kind the glass used ought to be very strong to resist the expansion caused by the explosion.

247. Having spoken of the decomposition of water by means of the electric fluid, it may be proper just to notice the process of forming water from the gases that compose it, by the action of the same agency. For this curious experiment Mr. Singer employed the apparatus represented in fig. 9, which consists of a stout globe of glass, with a stop-cock, having a wire passing through its centre to within a short distance of the cap to which the stop-cock is screwed. The globe must be exhausted by means of an air-pump, and then screwed on a receiver containing a mixture of oxygen and hydrogen gases, furnished with a

MIXED GASES.

Atmospheric air and hydrogen
Oxygen and hydrogen
Chlorine and hydrogen

Muriatic acid and oxygen

Carbonic oxide and oxygen

Nitrogen and oxygen
Sulphurous acid and oxygen
Phosphureted hydrogen and oxygen
Sulphureted hydrogen and oxygen
Oxygen and ammonia

100 olefiant gas and 284 oxygen
100 olefiant gas and 100 oxygen

stop-cock. When the cocks are opened, the globe will be filled with the gases; they must then be shut, and a spark passed from the wire in the inside of the globe to the cap. A bright flash follows, and the inside of the globe becomes covered with moisture; the cocks are then to be opened, and more gas will rush into the globe. The cocks being again closed, a second explosion may be made, which will increase the dew on the inside of the globe; and the experiment may be repeated in this way until drops of water may be observed.

248. Such experiments as the preceding naturally led to numerous others on various liquids and also on different gaseous bodies: to detail these would be foreign to our purpose; yet to pass them over in silence would be to do them injustice. We shall, therefore, merely give the results of some remarkably fine experiments by Cavendish, and others, as drawn up in a tabular form by Mr. Singer. The numbers prefixed to some of the gases indicate the proportionate measures employed of each.

The results marked with a star are given on the authority of Dr. Henry and Mr. Dalton. In making the above experiments when the mixture consisted of inflammable gases with oxygen, the change was usually effected by a single spark; but in other cases it was found necessary to continue the current of sparks for many hours.

ELECTRICAL CONFIGURATIONS.

249. This is a most interesting and curious branch of mechanical electricity, and one which certainly challenges a more vigorous enquiry than has hitherto been made respecting it. It is thought by some that the experiments which we shall here briefly notice afford satisfactory proof that electricity is the real cause of crystallisation. The subject seems to have been first noticed by pro

fessor Lichtenberg, of Gottingen, and afterwards by Mr. Bennet, Cavallo, and others.

250. Excite a plate of any resinous substance, as gum-lac, by friction, and let any metallic body of any shape whatever, a brass ting for instance, be placed upon the plate. Let the ring be then electrified with an electricity opposite to that of the plate, and afterwards removed from the plate by a stick of sealing-wax, or any other non-conductor. Let some powdered resin be now shaken upon the plate, then if the plate has been excited negatively, and the brass ring positively, the powder will fall only on those points of the plate that were touched by the ring, and will form radiating appearances resembling stars, while almost no powder will be found on any other part of the plate. If, on the other hand, the

plate has been electrified positively, while the ring was electrified negatively, the powdered resin will fali only on the parts of the plate which were formerly uncovered, the figures being now indicated by the absence of the powder..

251. Mr. Bennet who repeated with much care the experiments of Lichtenberg, has given the following account of the method which he adopted for rendering figures produced in this way permanent. When it is wished to make the figures red, Take a pound of rasped Brasil wood; put it into a kettle with as much water as will cover it, or rather more: also put in about an ounce of gum arabic, and a piece of alum about the size of a large nut; let it boil about two hours, or till the water be strongly colored; strain off the extract into a broad dish, and set it in an iron oven, where it is to remain till all the water be evaporated, which with me was effected in about twelve hours; but this depends on the heat of the oven, which should not be so hot as to endanger its burning. Sometimes I have boiled the strained extract till it was considerably inspissated before it was placed in the oven, that it might be sooner dry.

252. When it is quite dry, but not burnt, scrape it out of the dish, and grind it in a mortar till it be finely pulverised. In doing this, it is proper to cover the mortar with a cloth, having a hole through it for the pestle, to prevent the powder from flying away and offending the nose, and also to do it out of doors if the weather be dry and calm, that the air may carry away the powder necessarily escaping, and which other wise is very disagreeable. When ground, let it be sifted through a fine hair sieve, returning the coarser part into the mortar to be ground again.

253. The plate I have mostly used, was composed of five pounds of resin, half a pound of bees'-wax, and two ounces of lamp-black, melted together, and poured upon a board sixteen inches square, edged round with slips of wood, at least half an inch high, to confine the composition whilst fluid: the plate was thus half an inch thick, which is better than a thinner plate, the figures being more distinct. After the composition is cold, it will be found covered with small blisters, which may be taken out by holding the plate before the fire till the surface be a little melted, then let it cool again; and upon holding it a second time to the fire, more blisters will appear; but by thus repeatedly heating and cooling the surface, it will at last become perfectly smooth. Some plates were made smaller, and the resinous composition confined to the form of an ellipsis, a circle, or escutcheon, by a rim of tin half an inch broad, and fixed upon a board.

254. The next thing to be done is to prepare the paper, which is to be softened in water, either by laying the pieces upon each other in a vessel of cold water, or first pouring a little hot water upon the bottom of a large dish; then laying upon it a piece of paper, so that one edge of the paper may lie over the edge of the dish, to remain dry, that it may afterwards be more conveniently taken up. Then pour more hot water upon its upper surface. Upon this place another

piece in the same manner, again pouring on more water, and thus proceed till all the pieces are laid in. By using hot water, the paper will be softened in a few minutes.

255. When the figures are to be made, the resinous plate must le horizontally, whilst the electricity is communicated, if the experiment requires any thing to be placed upon the plate: but it is convenient afterwards to place it in a vertical position whilst the powder is projected, lest too much powder should fall where it is not required.

256. A little of the powder may be taken between a finger and thumb, and projected by drawing it over a brush; or, what is better, a quantity of it may be put into the bellows and blown towards the plate. When the figure is sufficiently covered with powder, let the plate be again laid horizontally upon a table; then take one of the softened papers out of the water by its dry edge, and lay it carefully between the leaves of a book, pressing the book together, and permitting it to lie in this situation about half a minute. Then remove the paper to a dry place in the book, and press it again about the same time, which will generally be sufficient to take off the superfluous moisture. Then take up the paper by the two corners of its dry edge, and place the wet edge a little beyond the figure on the resinous plate, lowering the rest of the piece gradually till it covers the figure without sliding; then lay over it a piece of clean dry paper, and press it gently; let it remain a short time, and then rub it closer to the plate with a cloth; or, which is better, press it down by means of a wooden roller covered with cloth, taking care that the paper be not moved from its first posi

tion.

257. When the paper is sufficiently pressed, let it be taken up by its dry edge, and laid upon the surface of a vessel of water, with the printed side downwards; by this means the superfluous powder will sink in the water, and the figure will not be so liable afterwards to spread on the paper. After the paper has remained on the water a few minutes, take it up and place it between the leaves of a book, removing it frequently to a dry place. If it be desired that the paper should be speedily dry, let the bookleaves in which it is to be placed be previously warmed, and by removing it to several places it will be dry much sooner than by holding it near a fire. By the above process, it is obvious that leather, calico, or linen, as well as paper, may be printed with these figures, and the effects of the diffusion of electricity upon a resinous plate be exhibited to those who have not leisure or inclination to perform the experiments.'

258. To the above it may be proper to add, : that with a resinous plate of the kind now described, a very beautiful exhibition may be made of the different powers of positive and negative electricity. For this purpose prepare equal quantities of red lead and resin, by weight, finely powdered and intimately mixed, by being sifted together through a fine hair sieve. Put this powder into a bottle of India rubber for use. Let now a small jar be charged at the positive conductor of the machine, and, with its knob,

quickly write the letter P on the resinous plate: take the bottle containing the mixed powders, and by gently striking the sides of it between the palms of the hands, the mouth of it being directed towards the plate, which must be placed in a vertical position, project on the electrified part a little of the powder, and the letter will instantly appear, well defined, and covered with the red lead, while the resin will be dispersed. If now the whole be wiped clean off, and, with a jar charged at the negative conductor, the letter N be written on the plate, and the powder projected as before, it will be found that the negative electricity has selected the resinous particles for the formation of the letter, while those of the red lead have been rejected.

MAGNETIC EFFECTS OF ELECTRICITY.

259. The connexion between magnetism and electricity will be fully treated of in a subsequent part of this article; at present we shall merely offer the following general remarks in the way of showing the amount of what was known on the subject previously to the interesting discoveries recently made.

260. Dr. Franklin appears to have been the first who paid any serious attention to this subject. He sent the charge of some large electrical jars through fine sewing-needles; the ends of the needles were rendered blue, and on being carefully laid on water they traversed, evincing evident proofs of polarity. The most remarkable circumstance attending these experiments was, that if the needle lay east and west when the charge was passed through it, the end which was entered by the fluid pointed to the north: but if it lay south and north, the end which lay pointing to the north would continue to do so, whether the charge entered by that end or the other; although the Dr. imagined that a still stronger charge would have reversed the poles, even in that situation, since this effect had been actually produced by lightning. The polarity he also found to be strongest when the needle received the charge while lying north and south, and weakest when it lay so as to point east and

west.

261. But the experiments most to be relied on were made by Van Marum with the large machine and battery in the Tylerian museum at Haarlem. He and his assistants tried to give polarity to needles made of watch-springs, of from three to six inches in length; and also to steel bars nine inches long, from a quarter of an inch to half an inch broad, and about a line in thickness. The result was, that when the bar was placed horizontally in the magnetic meridian, whichever way the shock entered, the end of it that stood toward the north acquired the north polarity, and the opposite end acquired the south. If the bar, before it received the shock, had some polarity. and was placed with its poles contrary to the usual direction, its natural polarity was uniformly diminished, and often reversed; so that the extremity of it, which in receiving the shock pointed to the north, became the north pole, &c.

262. When the bar was struck standing perpendicularly, its lowest end became the north

pole in any case, even when the bar had previ ously some magnetism, and was placed with the south pole downwards. Things remaining the same, the bars seemed to acquire an equal degree of magnetic power, whether they were struck whilst standing horizontally in the magnetic meridian, or perpendicular to the horizon. When the needle was placed in the magnetic equator, whichever way the charge entered, it never produced any magnetism; but if it was passed through its width, then the needle acquired a considerable degree of magnetismi, and the end which lay towards the west became the north pole, and the other end the south pole. If a needle or bar, already magnetic, or a real magnet, was struck in any direction, its power was always diminished. For this experiment they used considerably large bars, one of which was 7.08 inches long, 0-26 broad, and 0-05 thick. When the shock was so strong in proportion to the size of the needle, as to render it hot, then the needle generally acquired no magnetism at all, or very little. These experiments were made with the power of a battery composed of 135 phials, containing among them about 130 square feet of coated surface.

MEDICAL ELECTRICITY.

263. The very remarkable properties of the electric fluid seem to have occasioned the application of its powers to organised bodies at an early period of its history; and the results, whether real or imaginary, gave rise to various opinions, which are now only viewed as monuments of credulity and imposture. It is not our intention to enter here minutely into an investigation of this department of the science of electricity; yet, although this would be improper on several grounds, we must not pass it over in silence. The application of electricity as a medical agent has recently been much revived; but that application is, we believe, most successfully made in the form of Voltaic electricity; and will therefore fall, with more propriety, under consideration in another place. From the numerous respectable testimonies extant, as to the real utility of electricity in the healing art, we shall make a choice selection, which it is hoped will satisfy the reader, that in the hands of a skilful operator, it may be applied in numerous instances with certainty of success. however be observed that no one ought to attempt its application who is not thoroughly conversant with the use of the apparatus, and capable of forming a correct judgment, as to the strength and duration of the application.

Let it

264. Speaking of the power of the apparatus which ought to be used in the application of electricity for medical purposes, Mr. Singer justly remarks, that the machine employed ought to be such as will furnish a constant stream of sparks; if a plate machine, it ought to be two feet in diameter; if a cylinder machine, not less than ten inches, and fourteen if possible. Machines called medical electrical machines, are sometimes made on a very small scale, and hence the application of them only produces trouble, waste of time, and final disappointment.

265. In connexion with a powerful electrical

machine, the auxiliary apparatus requisite for medical purposes are the following:-A jar fitted up with Lane's electrometer, by which shocks may be given of any required force. A pair of directors, each consisting of a glass handle, surmounted by a brass cap with a wire of a few inches in length, having a ball screwed on its extremity, which may be occasionally unscrewed and a wooden point substituted for it. When shocks are given by means of these directors, they must be applied at the opposite extremities of the part through which the charge is required to pass; and being respectively connected by conducting wires, the one with the outside of the jar and the other with the receiving ball of the electrometer previously placed at the requisite distance, the jar may be set to the machine, which is then put in motion until any required number of shocks has been given.

266. The insulated director is also employed to give sparks, being held by its glass handle, and its ball previously connected with the conductor by a fine chain being brought near the patient, or rubbed lightly over a piece of flannel or woollen cloth laid on the affected part. When the eye or any delicate organ is electrified, the ball of the insulated director is unscrewed and the wooden point applied, at the distance of about half an inch from the part. The stream of electricity which passes from the point, in such cases, produces rather a pleasant sensation than

otherwise.

267. An insulated stool is sometimes employed; it should be of sufficient size to receive a chair upon it, with a resting place in front of the chair for the feet. The patient being placed on the insulated chair, and connected with the conductor of the machine by means of a chain, sparks may be drawn from any part of the body by a person who stands on the ground and presents a brass ball to it.

afford relief; and about one in five are permanently cured. 8. Opacity of the cornea. This is sometimes cured by the long continued action of electricity thrown for ten minutes a day on the eye by a wooden point. When caused by the small-pox, it is said to yield most readily. 9 Gutta serena. The method of electrifying for opacity of the cornea has been successful in some instances of gutta serena; but there are numerous unsuccessful cases. 10. Amenorrhæa Cases of suppressed menstruation are generally relieved by sparks and slight shocks; but in retention of the menses electricity has been triec without success. 11. Knee cases. In instances of pain and swelling of the knee, the application of sparks has been effectual in about one case in ten. 12. Chronic rheumatism. Very numerous are the instances of success; the usual application is by sparks, for ten or fifteen minutes every day. In recent cases, a few days is sometimes sufficient; but in those of long standing, very considerable perseverance is often required. 13. Acute rheumatism. In one case out of six a cure was effected in about a month by the application of electricity. 14. Palsy. Moderate shocks, with sparks, have been occasionally successful in about one case of paralysis in every fourteen that have been tried. 15. St. Vitus's dance has been frequently relieved by electricity. There are indeed scarcely but few

diseases in which some successful instances of its application are not recorded; but we are still in want of a scientific examination of the statements that have been made on this subject.

269. It appears that the nerves are most powerfully affected by electricity, since the effect of a discharge sent through the body is always most conspicuous in their direction. When the charge of a battery is sent through the head of a bird, the optic nerve is generally found to be injured, and often completely destroyed; a like discharge sent through a larger animal is found to produce a universal protraction of strength, with trembling and depression. Mr. Singer says he once accidentally received a considerable charge from a battery, through the head, which produced the sensation of a violent but universal blow, followed by a transient loss of memory and indistinctness of vision, but was unattended by any permanent injury.

270. Mr. Morgan, who paid considerable attention to medical electricity, has remarked, that if the diaphragm be made to form part of the circuit of a coated surface equal to two feet, fully charged, the lungs make a sudden effort, which is followed by a loud shout; but that if the charge be small, it never fails to produce a violent fit of laughter; and that even those whose calmness and solemnity are not easily disturbed by ludicrous occurrences, are seldom able to withstand the powers of electricity. The first effect of a strong charge on the dia phragm is frequently followed by involuntary sighs and tears, and sometimes by a fainting fit. If the charge be passed through the spine, it produces a degree of weakness in the lower extremities; so that if a person be standing at the time, he sometimes drops on his knees, or fans prostrate on the floor.