minated by pointed pieces of charcoal, instead of balls. When a globe of this kind has been exhausted and filled with sulphureted hydrogen, on taking the Voltaic spark in it, the sulphur is separated, and deposited on the interior of the globe, and produces, during its separation, a very beautiful appearance.

217. Some other compound gases are similarly affected; phosphorus separates from phosphureted hydrogen, and arsenic from arsenureted hydrogen.

218. With the most powerful Voltaic batteries the striking distance of the spark, or interval at which it passes from one conductor to another, is very considerable. Mr. Children measured this effect by means of a micrometer, attached to two polished points of platina, which were inserted in a receiver containing very dry air. With 1250 pairs of plates the points were brought within one-fifteenth of an inch of each other before the spark took place. With a large apparatus employed at the London Institution, which extends to 2000 pairs of four-inch plates, points of charcoal were brought within a thirtieth or fortieth of an inch of each other before any light was evolved; but, when the points of charcoal had become intensely ignited, a stream of light continued to play between them when they were gradually withdrawn even to the distance of nearly four inches. The stream of light was in the form of an arch, broad in the middle and tapering towards the charcoal points; it was accompanied by intense heat, and immediately ignited any substance introduced into it; fragments of diamond, and points of plumbago disappeared, and seemed to evaporate, even when the experiment was made in an exhausted receiver; though they did not appear to have been fused. Thick platina wire melted rapidly, and fell in large globules; the sapphire, quartz, magnesia, and lime, were distinctly fused.

219. In rarefied air, the discharge took place at a greater distance, and the beam of light was made to pass through an interval of six or seven inches.

220. These phenomena may be exhibited on a smaller scale by means of 100 pairs of plates, of six inches square, an apparatus which is well suited for all experiments of fusion and ignition.

221. The arched form of the stream of light, passing between two charcoal points, is often very perceptible when the distance of the points does not exceed half an inch.

222. From the low intensity of the most powerful Voltaic apparatus, but little attention to insulation is required in the transmission of its effects. The conductors employed for this purpose consist of copper wires passed through a short piece of glass tube, which serves as an insulator to hold them by. Such conductors are represented attached to the battery, and placed on a glass plate to inflame gunpowder, at fig. 2.

223. As the charcoal points usually become ignited when the battery has moderate power, almost any combustible substance may be inflamed, if placed between them. Oils, alcohol, ether, and naphtha, are decomposed when the

points are plunged into them, and inflamed when they are brought near each other upon the surface.

224. Some of the most pleasing effects of the Voltaic apparatus result from its action on metals; if these substances, in thin leaves, are made the medium of communication between the opposite ends of a powerful battery, they inflame, and by continuing the contact may be made to burn with great brilliance. The best method of performing these experiments, is to suspend the metallic leaves to a bent wire proceeding from one extremity of the battery, and to bring in contact with them a broad metal plate connected with the opposite extremity; the brilliancy of the effect may be increased by covering the plate with gilt foil. Gold leaf burns with a vivid white light tinged with blue, and produces a dark brown oxide. Silver leaf emits a brilliant emerald-green light, and leaves an oxide of a dark gray color. Copper produces a bluish-white light attended by red sparks; its oxide is dark brown. Tin exhibits nearly similar phenomena; its oxide is of a lighter color. Lead burns with a beautiful purple light; and zinc with a brilliant white light, inclining to blue, and fringed with red. For the distinct appearance of these colors it is essential to make the contacts with the metal; for, if charcoal be used, the brilliant white light it evolves absorbs the colors produced by the combustion of the metals.

225. If a fine iron wire be connected with one extremity of a powerful battery, and its end be brought to touch the surface of some quicksilver connected with the other extremity, a vivid combustion both of the wire and the quicksilver results, and a very brilliant effect is produced.

226. If a fine iron wire of moderate length be made the medium of connexion between the extremities of the battery, it becomes ignited, and may be fused into balls; or if a platina wire is employed, it may be kept at a red, or even white, heat, for a considerable length of time; which seems to prove that some power is continually circulating through it; but however powerful the battery, wires are never dispersed by it, as they are by the action of a charged surface.

227. If the slender wire be inserted in any fluid, and then introduced into the Voltaic circuit, the fluid may be made to boil.

228. It has been noticed, that, if any two wires of different thicknesses are taken, on either of which a certain battery can produce ignition, a greater length of the thickest wire will be ignited than of that which is thinner. This effect may probably arise from the cooling influence of the air, for the surface of the thin wire is most extensive in proportion to its quantity of metal; and that the surrounding medium has an influence on the degree of ignition may be proved by another experiment.

229. Stretch a fine wire of platina, withinside a glass receiver, placed upon an air-pump, so that the air surrounding the wire may be removed or restored at pleasure. Ignite the wire to a dull red heat, by connecting its opposite extremities with the wires from a Voltaic battery, of sufficient power for that purpose.

Rarefy the air by the action of the pump; and as the rarefaction proceeds, the ignition of the wire will become more vivid, until at length it obtains a glowing white heat. Admit air into the receiver, and the wire will lose its intense heat, and appear more dull than at first. Rarefy the air again, the ignition will increase. Restore it to its original density, it will again diminish. These effects may be repeated many times, and will maintain the same proportion to each other, though they are less intense at each repetition.

230. The power of a Voltaic apparatus increases with the number of plates it contains, within certain limits, but the limit is different for the various effects it produces, and varies also with the manner of employing the appa

ratus.

231. The effects have been stated by Volta to be in the simple ratio of the numbers, but very limited series only had been put together at the time this statement was made, and there appears to be a loss of power when very extensive arrangements are employed. The pure electrical effects, and the force of the shock, are found to increase with the number, and an arrangement of 1500 may be employed. The power of chemical decomposition, and transfer, also continues to increase with the number when the battery is excited by dilute acid; but, if it be charged with river water, the power does not increase after 400 or 500 plates. The powers of ignition have increased in exact proportion to the numbers within the limit of 100 plates, beyond that himit there appears to be a loss of power; for Sir H. Davy found that 100 plates ignited three inches of platina wire, one-seventieth of an inch diameter, and 1000 similar plates, charged in the same way, ignited only thirteen inches.

232. The French chemists have investigated the ratio of increase for different numbers of plates, as indicated by the quantity of gas liberated by the decomposition of water; and they announce that the increase is as the cube root of the number of plates. The apparatus they employed, was arranged in the form of troughs of a particular construction, being part of a large apparatus constructed by order of the French government. Sir H. Davy states, that he has made similar experiments with the large combination of porcelain troughs, employed in the Royal Institution, and the results he obtained indicate an increase nearly as the squares

of the numbers.

233. The result of every experiment of the kind must be uncertain if a series of minute attentions are not observed, which appear to have been overlooked in those already instituted. The vessels employed for the decomposition should be of the same size and form; the wires of the same length and thickness, and placed at equal distances from each other, in a fluid of uniform conducting power.

234. When the size of the plates is increased, their effects on perfect conductors, such as metals, charcoal, and strong acid solutions, are greatly augmented; but their action on imperfect conductors, as water, and various weak saline solutions, remains unaltered. If a battery, for instance, of thirty pairs of plates of

two inches square, be compared with another battery of thirty plates, of six inches square, charged with diluted acid of the same strength; there will be no material difference in the shock they produce, or the quantity of water they decompose in a given time; but the small battery will not melt wire, or burn metals, and will scarcely produce a spark between two points of charcoal; whilst the large battery will evolve a brilliant light between the charcoal points, deflagrate metallic leaves with rapidity, and ignite several inches of wire.

235. This remarkable fact, which appears to have been first noticed by the French chemists, is susceptible of some explanation (on the supposition that the phenomena are electrical). If a Leyden jar, for instance, having a square foot of coated surface, be applied to an electrical machine with another jar, whose coated surface is equal to four square feet; after a certain number of turns of the machine, they will both be charged, and to the same intensity, for they will equally affect an electrometer. But the large jar will contain four times the quantity of electricity that the small one does, and will fuse sixteen times the quantity of wire.

236. Now, suppose an imperfect conductor, capable of transmitting only such a quantity of electricity as is adequate to the charge of half a square foot; and it is obvious either of the jars before mentioned would produce the same effect on such a substance; for they both contain more than it can transmit, and its conducting power, which remains the same in both cases, limits the effect that can be produced by either. It is consequently found, that, if several different sized jars are charged to the same degree, the shock is nearly equally painful when received from either of them.

237. Mr. Cavendish has stated, that 'iron wire conducts 400,000,000 times better than rain or distilled water; that is, the electricity meets with no more resistance in passing through a piece of iron wire 400,000,000 inches long, than through a column of water of the same diameter only one inch long. Sea water, or a solution of one part of salt in thirty of water, conducts 100 times, and a saturated solution of sea salt about 720 times better than rain water.' It is therefore probable, that the power excited by a Voltaic apparatus, with plates of two inches square, is in quantity equal or superior to the conducting capacity of most aqueous fluids, and consequently no increased effect can be produced on such fluids by larger plates, which increase the quantity of that power, but not its intensity. But if a conductor be presented to the large plates, which is capable of receiving the increased quantity furnished, the effect must necessarily be greater on such conductors, in proportion to the increased impulse it may be supposed to receive. These facts are capable of easy illustration.

238. Let two wires, proceeding from the extremities of a battery of fifty or 100 plates of two inches square, be plunged in separate glasses of water, if the glasses are connected by putting a finger into each of them, a shock will be felt at the moment of contact. Connect the water

in the glasses by some fibres of moistened cotton, or by an inverted syphon filled with water; on repeating the contact with this arrangement, either no shock, or a very slight one will be felt. Make a similar experiment with another battery of the same extent, but with plates of six inches square. The shock will be nearly as great when the glasses are connected by moistened fibres, as when no connexion exists between them; and whilst the circuit exists through the moistened fibres, and the human body, if a third circuit be formed through a fine wire, several inches of it may be ignited. The imperfect conductors being incapable of conducting more than a small portion of the power excited by the large plates.

239. Whatever be the cause of the power of the Voltaic apparatus, the quantity of that power excited by any given number of plates under similar circumstances, will be in direct proportion to the size of the plates; and if the power be electricity, or should obey the same law that operates with charged surfaces, the comparative action of different sized batteries, containing the same number of plates, should be, with regard to their power of igniting wire, in the proportion of the square of the increased surface; thus if two batteries are taken, one containing fifty plates of twenty square inches surface, and the other fifty plates of forty square inches, the latter ought to ignite four times the length of wire the former can ignite. From some experiments with plates of four inches square, and others with plates of eight inches square, made many years since, it has been stated by Dr. Wilkinson, that the power of ignition, in batteries of the same total surface, but with plates of different sizes, increases in the proportion of the squares of the surfaces of the elementary plates, singly taken in each.' It was afterwards shown by Mr. Harrison of Kendal, that when the total surfaces are not equal, the rate of ignition must be as the sixth power of the diameters of the elementary plates, or as the cubes of their respective surfaces.

240. It appears also from some experiments with large plates, mentioned by Sir H. Davy, that the power of ignition, for equal number of plates, probably increases in a higher proportion than the squares of their surfaces; for twenty double plates, each exposing a surface of eight square feet, ignited more than sixteen times as much wire as twenty double plates, having each a surface of two square feet.

241. Several curious galvanic experiments and observations have been published by M. Bichat, author of a very celebrated work on anatomy. In speaking of the influence of the destruction of the brain on that of the heart, after having proved, conformably to observation and experience, that it is not immediately by the interruption of the cerebral action that the heart ceases to act, he confirms this fundamental datum of physiology and pathology, by a series of galvanic experiments, which demonstrate that the heart is in all cases independent of the brain.

242. These experiments,' he observes, 'were made by me with the most scrupulous attention, because several very respectable authors have

recently advanced an opinion contrary to mine and have endeavoured to prove that the heart, together with the other muscles of organic life, do not differ, as to their susceptibility to the galvanic influence, from the different muscles of animal life. I shall begin by a detail of the observations I have made on animals with red and cold blood.

243. (1.) In several experiments made on frogs, I coated the brain, on the one hand with lead, and the heart and muscles of the inferior extremities, on the other, with a long lamina of zinc, the upper end of which touched the heart, and the lower end the muscles. Having, by the means of silver, established a communication between the coatings of the muscles and those of the brain, the movements of the limbs constantly followed; but I could not perceive any acceleration in the contractions of the heart, when it still continued to beat; and, when its action had entirely ceased, it did not display the smallest movement. Whichever may be the voluntary muscle that is coated at the same time with the heart, with a view to a comparison of the phenomena they exhibit at the moment of the metallic communication, there is constantly a marked and decided difference.

244. (2.) In the case of other frogs, I coated, with a common metallic wire, on the one hand, the cervical part of the spinal marrow, in the upper region of the heart, to the end that the coating might be above the part where the nerves which proceed from the great intercostal nerve, and thence to the heart, originate; and, on the other hand, the heart, and any one of the voluntary muscles. I constantly noticed a result similar to the one which attended the preceding experiment, whenever the communication was established. There were invariably violent agitations in the voluntary muscles, without any visible alteration in the contractile movements of the heart.

245. (3.) I endeavoured to denudate the nerves which lead to the heart of frogs. Several grayish filaments, scarcely perceptible, with the nature of which I must acknowledge I am not positively acquainted, were coated with a metallic substance, at the same time that the heart was made to rest on a substance of a similar nature. When the communication was established by the means of a third metal, not the smallest sensible effect was to be perceived.'

246 Dr. Wilson Philip has made some curious experiments on the influence of the Voltaic battery in obviating the effects of the division of the eight pairs of nerves. In some experiments in which the nerves of the eighth pair were divided in the neck of a rabbit, and the ends not displaced, and the animal was allowed to live some hours, it was found that food swallowed immediately before the division of the nerves, was considerably digested, even when the divided ends of the nerves had separated to the distance of a quarter of an inch from each other.

247. In other experiments in which, after the division of the nerves, the divided ends had been turned completely away from each other, little or no perfectly digested food, when the animal

was allowed to live some hours, was found in the stomach: and the longer the animal lived, the smaller was the proportion of digested food in the stomach, the great mass having the appearance of masticated food, which was not sensibly lessened in quantity, however long the animal lived. In an experiment in which, under some circumstances, the stomach was exposed, from the time of the division of the nerves, to the influence of a Voltaic battery sent through the lower portion of the divided nerves, its contents were apparently as much changed as they would have been in the same time in the healthy animal. The change was also of the same kind, the contents of the stomach assuming a dark color, and those of the pyloric end being more uniform, and of a firmer consistence than those of the central and cardiac portions of the stomach, while the whole contents became less in quantity. 248. The division of the nerves, in both ways, produced difficulty of breathing and efforts to vomit; neither of which occurred, when the stomach and lungs were brought under the influence of a Voltaic battery, sent through the lower portion of the divided nerves.

249. When, under the foregoing circumstances, the lungs had not been exposed to the Voltaic influence, and the animal had been allowed to live for five or six hours, they were found much affected in the rabbit which had been submitted to this influence, they seemed quite healthy.

250. An account of some very interesting experiments performed by Dr. Ure, on the body of a criminal executed in the north, was read before the Glasgow Literary Society. The paper commences with some appropriate general physiological views relating to the application of galvanism, in which the author notices particularly the researches of Dr. Wilson Philip on the relation between Voltaic electricity and the phenomena of life. The author gives the following detail of his experiments.

251. The subject of these experiments was a middle-sized, athletic, and extremely muscular man, about thirty years of age. He was suspended from the gallows nearly an hour, and made no convulsive struggle after he dropped; while a thief executed along with him, was violently agitated for a considerable time. He was brought to the anatomical theatre of the University of Glasgow in about ten minutes after he was cut down. His face had a perfectly natural aspect, being neither livid nor tumefied; and there was no dislocation of his neck.

252. Dr. Jeffrey, the distinguished professor of anatomy, having on the preceding day requested me to perform the galvanic experiments, I sent to his theatre with this view, next morning, my minor Voltaic battery, consisting of 270 pairs of four-inch plates, with wires of communication, and pointed metallic rods with insulating handles, for the more commodious application of the electric power. About five minutes before the police officers arrived with the body, the battery was charged with a dilute nitro-sulphuric acid, which speedily brought it into a state of intense action. The dissections were skilfully executed by Mr. Marshall, under the superintendence of the professor.

253. Experiment I.—A large incision was mad into the nape of the neck, close below the occiput. The posterior half of the atlas vertebra was then removed by bone forceps, when the spinal marrow was brought into view. A considerable incision was at the same time made in the left hip, through the great gluteal muscle, so as to bring the sciatic nerve into sight; and a small cut was made in the heel. From neither of these did any blood flow. The pointed rod connected with one end of the battery was now placed in contact with the spinal marrow, while the other rod was applied to the sciatic nerve. muscle of the body was immediately agitated with convulsive movements, resembling a violent shuddering from cold. The left side was most powerfully convulsed at each renewal of the electric current. On moving the second rod from the hip to the heel, the knee being previously bent, the leg was thrown out with such violence as nearly to overturn one of the assistants, who in vain attempted to prevent its extension.

Every

254. Experiment II.-The left phrenic nerve was now laid bare at the outer edge of the sternothyroideus muscle, from three to four inches above the clavicle; the cutaneous incision having been made by the side of the sterno cleido-mastoideus. Since this nerve is distributed to the diaphragm, and since it communicates with the heart through the eighth pair, it was expected by transmitting the galvanic power along it, that the respiratory process would be renewed. Accordingly, a small incision having been made under the cartilage of the seventh rib, the point of the one insulating rod was brought into contact with the great head of the diaphragm, while the other point was applied to the phrenic nerve in the neck. This muscle, the main agent of respiration, was instantly contracted, but with less force than was expected. Satisfied, from ample experience on the living body, that more powerful effects can be produced in galvanic excitation, by leaving the extreme communicating rods in close contact with the parts to be operated on, while the electric chain or circuit is completed, by running the end of the wires along the top of the plates in the last trough of either pole, the other wire being steadily immersed in the last cell of the opposite pole, I had immediate recourse to this method. The success of it was truly wonderful. Full, nay laborious breathing instantly commenced. The chest heaved, and fell; the belly was protruded, and again collapsed, with the relaxing and retiring diaphragm. This process was continued, without interruption, as long as I continued the electric discharges.

255. 'In the judgment of many scientific gentlemen who witnessed the scene, this respiratory experiment was perhaps the most striking ever made with a philosophical apparatus. Let it also be remembered, that, for full half an hour before this period, the body had been well nigh drained of its blood, and the spinal marrow severely lacerated. No pulsation could be perceived meanwhile at the heart or wrist; but it may be supposed that, but for the evacuation of the blood, the essential stimulus of that organ, this phenomenon might also have occurred

256. Experiment III.-The supra-orbital nerve

257. Experiment. IV.-The last galvanic experiment consisted in transmitting the electric power from the spinal marrow to the ulnar nerve, as it passes by the internal condyle at the elbow; the fingers now moved nimbly, like those of a violin performer; an assistant, who tried to close the fist, found the hand to open forcibly, in spite of his efforts. When the one rod was applied to a slight incision in the tip of the fore-finger, the fist being previously clenched, that finger extended instantly; and, from the convulsive agitation of the arm, he seemed to point to the different spectators, some of whom thought he had come to life!'

258. An hour was spent in these experiments, when an experiment was made with the view of determining the quantity of residual air in the lungs; after the detail of which, the author proceeds as follows.

259. In deliberating on the above galvanic phenomena, we are almost willing to imagine, that if, without cutting into and wounding the spinal marrow and blood-vessels in the neck, the pulmonary organs had been set a-playing at first (as I proposed), by electrifying the phrenic nerve (which may be done without any dangerous incision), there is a probability that life might have been restored. This event, however little desi-rable with a murderer, and perhaps contrary to law, would yet have been pardonable in one instance, as it would have been highly honorable and useful to science. From the accurate experiments of Dr. Philip, it appears that the action of the diaphragm and lungs is indispensable towards restoring the suspended action of the heart and great vessels, subservient to the circulation of the blood.

260. It is known that cases of death-like lethargy, or suspended animation from disease and accidents have occurred, where life has returned, after longer interruption of its functions than in the subject of the preceding experiments. It is probable, when apparent death supervenes from suffocation with noxious gases, &c., and when there is no organic defect, that a judiciously directed galvanic experiment will, if any thing will, restore the activity of the vital functions. The plans of administering Voltaic electricity hitherto pursued in such case, are, in my humble apprehension, very defective. No advantage, we perceive, is likely to accrue from passing electric

261. I would, however, beg leave to suggest another nervous channel, which I conceive to be a still readier and more powerful one to the action of the heart and lungs than the phrenic nerve. If a longitudinal incision be made, as is frequently done for aneurism, through the integuments of the neck at the outer edge of the sterno-mastoideus muscle, about half way between the clavicle and angle of the lower jaw; then, on turning over the edge of this muscle, we bring into view the throbbing carotid, on the outside of which the par vagum and great sympathetic nerve lie together in one sheath. Here, therefore, they may both be directly touched and pressed by a blunt metallic conductor. These nerves communicate directly or indirectly with the phrenic, and the superficial nerve of the heart is sent off from the sympathetic.

262.Should, however, the phrenic nerve be taken, that of the left side is the preferable of the two. From the position of the heart, the left phrenic differs a little in its course from the right. It passes over the pericardium, covering the apex of the heart.

263. While the point of one metallic conductor is applied to the nervous cords above described, the other knob ought to be firmly pressed against the side of the person, immediately under the cartilage of the seventh rib. The skin should be moistened with a solution of common salt, or, what is better, a hot saturated solution of sal ammoniac, by which means the electric energy will be more effectually conveyed through the cuticle, so as to complete the Voltaic chain.

264. To lay bare the nerves above described, requires, as I have stated, no formidable incision, nor does it demand more anatomical skill, or surgical dexterity, than every practitioner of the healing art ought to possess. We should always bear in mind that the subject of experiment is at least insensible to pain; and that life is at a stake, perhaps irrecoverably gone. And assuredly, if we place the risk and difficulty of the operations in competition with the blessings and glory consequent on success, they will weigh as nothing with the intelligent and humane. It is possible, indeed, that two small brass knobs, covered with cloth moistened with solution of sal ammoniac, pressed above and below on the place of the nerve and the diaphragmatic region, may suffice, without any surgical operation. It may first be tried.

265. Immersion of the body in cold water accelerates greatly the extinction of life arising from suffocation; and hence less hopes need be entertained of recovering drowned persons after a considerable interval, than when the vital heat has been suffered to continue with little abate