equivalent in heat, of the chemical actions taking place in those batteries. What is really required is, to determine in numbers some constant unit or coefficient for the force considered, and which could be easily obtained by each chemist. The most simple of batteries is Smee's the only chemical action normally going on in this being the oxidation and solution of zinc in the acid, with disengagement of hydrogen. The value of the heat corresponding to this action was carefully measured by M. Favre, and expressed by the number 18,444 for ordinary zinc, and 18,791 for zinc amalgamated. In preliminary researches with the battery named, including 125 determinations of its electro-motive force, M. Davy found variations in this force between 16,886 and 20,604, a difference of 2 per cent., where he had been led to expect no more than that of th part. The researches resulted in showing 7 causes of disturbance acting within the cup or battery, and leading to variations in the current force which, independently of all influences outside itself, it can generate. Of these, the most important appeared to be the presence of air in solution in the acidulated water, and the influence of the sulphate dissolved in the liquid during action of the battery; the oxygen of the former acting directly on the zinc, and preventing to a corresponding extent the decomposition of the water, and both causes operating to diminish the electric force of the battery. The third cause of disturbance was the influence of concentration of the acid, the force generated however being constant so long as the acid solution contained more than 25 equivalents of water for 1 of acid. The other influences were, that of purity of the zinc and state of the amalgam-the electric force from amalgamated zinc being generally stronger; that of purity of the acid -the nitrogen compounds often present in it increasing the strength of the current; that of the water-distilled water being preferable; and that of temperature, which causes considerable variation in the current generated. Finally, in order to secure results under uniform conditions, M. Davy works a Smee's battery consisting of a plate of platinized platinum immersed vertically in a mixture of sulphuric acid with 8 to 10 times its weight of distilled water, boiled to free it of air, this solution being placed in a vertical glass tube, at bottom of which is a liquid amalgam of pure zinc in pure mercury. A platinum wire traversing the bottom of the tube forms the negative pole of the element, the glass tube containing the arrangement is immersed in a large vessel full of water, which keeps the temperature constant, the liquid of the cell being also frequent ly changed. Fixed resistances in platinum of known temperatures being introduced into the circuit, serve to show the corresponding variations in intensity of the current. M. Davy takes for the electro-motive force of this pile the number 18,510. ("Philos. Magaz.," July, 1862.) Measures of Electrical Quantities.—Mr. Latimer Clark and Sir Charles Bright presented before the British Association, 1861, a paper on the principles which should be observed in measuring electrical quantities and resistance. They believe that four standards or units are in reality required, these being mutually dependent on each other; and that by the aid of these every conceivable form of electrical manifestation, whether static or dynamic, can be precisely expressed. These are: A. A unit of electrical tension, potential, or electro-motive force. B. A unit of electrical quantity, as applied to static electricity. C. A unit of electric current, or quantity in dynamic electricity. D. A unit of electrical resistance. As the unit of tension they propose that of one Daniell's element or cell, to be named 1 Ohma. As the unit of quantity of static electricity, they propose that corresponding to a tension of 1 Daniell's element existing between two coatings oppositely charged, the coatings being 1 millimetre apart, of 1 square metre surface, and separated by dry air; this quantity to be termed 1 Farad. As the unit of current, they propose that of one unit of quantity per second delivered along a conductor, as determined by the galvanometer; this to be known as 1 Galrat. But the wire that will conduct 1 unit of electricity in 1 second becomes conversely the standardor unit of resistance, this to be known as 1 Volt. Of these units, the first three will in practice require to be measured in multiples of 1,000 and 1,000,000 times the unit-indicated by the prefixes kilo- and millio-; the fourth, as too large for defining the resistance of telegraph conductors, will require to be measured in fractions of the unit-indicated again by the prefixes kilo-, millio-, and billio-. A synopsis of the paper at greater length is given in the "Journal of the Franklin Institute," February, 1862. Report on a proposed Standard of Electrical Resistance.-Mr. F. Jenkin, on behalf of a committee appointed by the British Association to consider this subject, reported at its last meeting. In such a standard five qualities are desirable; it should be of convenient magnitude; should form part of a general and coherent system of electrical measures; should bear a definite relation to the unit of work; should be unalterable; and should be reproducible, if accidentally destroyed. Of the units hitherto proposed, the committee conclude that none fulfil all these conditions. Those based on an arbitrary length and section, or weight of some material arbitrarily taken, lacked the first and second qualifications; the absolute system possessed these, but failed in the third and fourth; and the system of Messrs Bright and Clark also failed in the third particular. Not being able to advise the unqualified adoption of any of the previously proposed standards, the committee recommend that a material mètre seconds standard be prepared, and of such substance and form as to insure the most absolute permanency. The aim should be to make this standard correspond to a current force equal to 10,000,000,000 times the value given by the quotient of 1 metre by 1 second of time, that is, 101. and to this it should approximate as nearly as possible. Such a unit would not differ more than .03 for Dr. Siemens' mercury unit. It should not be called an absolute unit, but simply the "unit of 1862;" and it should not be constructed at all until a very close approximation to the absolute value was supposed to have been attained, and great permanency in the material standard secured. Then, as the advance of science showed more and more truly the actual deviation of this from the true unit intended, corrections could be made by experimenters in their results when required. The material standard itself, however, should under no circumstances be altered in substance or definition. Influence of Temperature on the Conducting Power of Metals.-Matthiessen and Van Bose presented before the Royal Society a paper on this subject, Jan. 16, 1862. They find that, contrary to what has been stated by Becquerel, Siemens, and others, the conducting power or the resistance of a metal for an electric current, does not increase or decrease in a direct ratio to the temperature, but in a ratio much more complex. All pure metals in the solid state, however, vary in conducting power to the same extent between the temperatures of 32° and 212° F. Wires of the same metal behave differently after being kept for some days heated to the same degree. Metalloids generally conduct better when heated than when cold; this is true of selenium, gas coke, graphite, and the gases. Mechanical Effects of Powerful Tension.-M. Faye exhibited before the Academy of Sciences, Paris, an experiment in which two plates of crown glass, respectively nearly 1 and 2 inches thick, were completely pierced through by the electric spark of the great induction machine recently constructed by M. Ruhmkorff. The path left by the spark is seen to consist of a white and opaque fillet, extremely slender, its whole length presenting bright places at slight distances, and taking different directions in the manner of the parts of a spiral. It shows no metallic deposit. In the thicker plate, at a depth of about, the track bifurcates; and near to the opposite face, it subdivides into many and more direct fillets. During the experiment, Ruhmkorff demonstrated by the appearance of Haidinger's colored rings, that the passage of the spark was accompanied by an energetic compression of the substance of the glass; but no trace of fusion appeared about the course taken by it. M. Faye thought nevertheless that, by passing the spark of this machine through some pulverulent substance somewhat more fusible than crown glass, true fulgurites could be produced. Study of the Electric Spark by Aid of Photography.-Prof. O. N. Rood, of Troy University, N. Y.; has been, by aid of a new and very neat method devised by him, studying the form and characteristics of the electrical spark. The photographic images of the electric spark hitherto obtained by Prof. B. Silliman, jr., Prof. W. B. Rogers, Feddersen and others, have been taken from a position at right angles to the course of the spark, thus furnishing a side view of it; and they have usually required a prolonged exposure of the sensitive surface to the light, in some instances from 3 to 6 minutes. Prof. Rood's method is that of receiving the spark directly upon a sensitive or properly prepared surface, and subsequently developing the figure produced, in the manner of photography. In this way he secures the figure corresponding to a single discharge of ordinary or frictional electricity, the brief duration of which has forbidden its being photographed by previous methods. His plan is an applica tion, first, of Becquerel's discovery that paper coated with bromide of silver is sensitive to the electric spark; and, secondly, of his own observation that, in instantaneous photography, the portions of the sensitive surface immediately contiguous to those acted on by the strong lights, still remained quite unaffected by the exposure. Upon testing the fact in case of a single electric spark, he found that an intense and sharply defined image, full of delicate details, was here also the result. The question whether these images were due to direct action of the electricity itself, or to the agency of the light evolved, appeared to be settled by certain experiments, especially by the fact that when the spark was received on a thin glass plate, placed over another coated with sensitive collodion, the electric image could be developed, though less sharply defined, on the second plate; but when the first or thin glass was blackened, no image on the second resulted, from one or a number of discharges. The form of apparatus given for these experiments is simple; the collodion recommended is that suitable for ambrotyping, and when freshly prepared. The general form of the positive electrical spark ascertained, is a combination of two figures: a star and one or more rings, all having nearly a common centre. The rings are usually quite within the limits of the star, sometimes one of them without it; and when two or more rings appear, they are successively darker toward the centre. The marked differences in form of the two components, and the fact that the annular form is characteristic of the electric brush, seem to indicate that each simple spark consists of two or more successive discharges of varying intensity. When, owing to distance, or to the use of a pointed wire, the partial sparks become more uniformly blended, the electrical "brush" is the result; and the figures confirm the general view of electricians on this point, by showing how the former passes by insensible gradations into the latter. The form of the negative spark differed greatly from that of the positive, being destitute of rays, generally circular in shape, and often made up of a number of minute circles placed without symmetry. For like distances it was also larger than the positive, and never nearly so well defined. Moreover, there is a general resemblance between the positive and negative figures as thus obtained, and the figures of the corresponding sorts obtained by Lichtenberg and Riess by passing the sparks to a surface sprinkled with powdered sulphur and red lead, and known as Lichtenberg's figures."-" Amer. Jour. of Science," March, 1862. Production of Vibrations and Musical Sounds by Electrolysis. If a large quantity of electricity be made to pass through a suitable good conducting electrolyte into a small surface of pure mercury, especially when the latter is disposed in a narrow band or ring, strong vibrations will occur, the surface of the mercury being thrown up into numerous crispations or minute ridges running in a radial direction, this appearance being often accompanied with definite musical sounds, and which can sometimes be heard to a distance of 50 feet. The best electrolyte or liquid employed to conduct the current (while undergoing decomposition by its action), is formed by dissolving 10 grs. of cyanide of mercury and 100 grs. of hydrate of potash, in 2 oz. of aqueous hydrocyanic acid, containing .05 of the anhydrous acid. The vibrations and sounds occur only at the surface of the mercury, which serves as the electrode. The only liquids giving the phonetic vibrations were solutions of alkaline cyanides, containing dissolved mercury (in combination), and these only when the electrodes, or at least the cathode (positive pole) was of mercury. The vibrations and sounds vary considerably according to the size and number of the voltaic elements. With a few cups only in the battery and the plates of large size, the vibrations were rapid and the tone high; with many pairs of small plates, the vibrations were less frequent and the tone low. The most suitable number of elements appeared to be 2 of Grove's, or 5 of Smee's battery. By interposing in the circuit made a coil of stout copper wire, the sounds became more bass, still more so upon thrusting an iron coil suddenly within this; but if, in either case, a secondary coil with its ends united were made to surround the former, the sound returned to the higher pitch and preserved it so long as the outermost coil remained in place. A strong electro-magnet placed in various positions in the neighborhood of the vibrations had no influence in the way of changing or arresting them. The phenomena were readily produced by connecting with the positive pole of the battery a circular pool of mercury 1 to 3 inches in diameter, and surrounding this with a ring of the same metal about in. wide, connected with the negative pole; the liquid metal being contained in suitable glass or gutta percha vessels, and covered with the solution to the depth of half an inch. Mr. G. Gore, by whom these investigations have been conducted, regards the vibrations as having an electro-chemical origin, and as resulting from an attraction between the mercury of the negative electrode and the mercury of the electrolyte. New Experiments in Electro-Magnetism.-M. Leroux, of the Polytechnic School, Paris, having a platinum wire about 3 of an inch in diameter, and 7 inches or more in length, rendered incandescent by being made part of an electrical circuit, presented the wire in this state and properly flexible to the poles of a powerful magnet or electro-magnet: the wire assumed a series of configurations, depending on the direction of the current and whether the line joining its extremities has a position axial or equatorial with reference to the magnet. Such a wire was attracted by a mass of iron, especially if the latter presented a large surface, a counterpart of Arago's experiment that a wire traversed by a current attracts iron filings. Leroux also showed how a fine conjunctive wire could be made to coil itself spontaneously around the pole of a magnet. Ĥaving fixed upon one of the poles of a horse-shoe magnet an armature of soft iron, about 4 inches in length, turned and polished, he attached to this armature the extremity of a silver wire, holding the other extremity in his hand, but so loosely that the wire could constantly obey the forces which solicited it. When this wire was then traversed by a current, it coiled itself around the armature, and there formed a helix wound in a direction opposite to that which would be required to give to the armature the same magnetism it already possessed. This experiment is more conveniently performed by having the wire at first coiled on a small metallic bobbin suspended above the magnet; and the more constant the length of wire traversed by the current, the less is the risk of burning it. Thus is found a new kind of motion obtained by the action of the pile. To prevent the undue acceleration of this motion, a smaller cylinder may be fixed on the axis of the bobbin, from which a small weight at the end of a silk thread draws in the direction opposite to that given to the bobbin by the uncoiling wire. For these experiments a current of about 10 Bunsen's elements was employed. Electricity Developed during Evaporation and Effervescence.-Prof. Tait and Mr. Wanklyn have, by use of the extremely sensitive and accurate divided ring electrometer of Prof. Thomson, investigated the phenomenon of development of electricity by evaporation of certain liquids, during the few moments in which on quitting the "spheroidal state" in a heated capsule or dish, and coming again in contact with its surface, they emit the well-known “fizzing" sound attending their rapid evaporation at that period. By conducting wires suitably arranged, in course of which the electrometer was placed, the strength of the charge generated could be estimated, and this is numerically expressed for the various liquids so examined, 5.8 being taken to represent the electro-motive force of a single Grove's element. The generated charges in case of some of the substances examined were as follows: Bromine, +400; iodine, +90; ammonia, -200; alcohol, -10; mercury, -75; water, -80; strong solution of common salt, -400; caustic potash, +150; strong nitric acid, +7.5; benzole and valerianic ether, no effect. From a like series of experiments on the development of electricity during brisk effervescence of different liquids, the following results were obtained: with solution of zinc in hydrochloric acid, — 750; solution of binoxide of manganese in hydrochloric acid, -150; solution of common salt in sulphuric acid, +10. (" Proc. Roy. Soc. Edinb.," Feb. 1862.) positive electric tension was the result; while, if the discharge was directed toward the earth, or to a distant region of the air, the tension became negative. The vapor which moved toward the observatory, if free from cinders, was strongly positive; but the cinders which fell when the smoke of a superior current deviated from the zenith were negative. II. APPLICATIONS.-Ritchie's Electrical Ma chines.-The principle of induction holds true for current as well as for common electricity; illustrations being found in the facts that if a wire or coil be made to transmit a gal vanic current while another wire or coil is situated in immediate relation with this, but not so as directly to receive the electricity from it, and if along the first wire or coil an interrupted or periodically reversed current be transmitted, then at every such interruption and recommencement, or reversal, of the pri mary current, a secondary or induced current will be developed in the second wire or coil; and this induced current will partake in a large degree of the properties of common electricity, having great intensity, and being capable of discharging itself to a corresponding distance through dry air or other non-conductor-a power of which the primary or inducing current is wholly destitute. If, further, the elec trical condenser be added at the extremity of the second wire, so as to intensify the charge arising in it at the moments of interruption, the intensity and mechanical effect of the induced current are still further increased. These principles were determined by the researches of Faraday, Henry, De la Rive, Fizeau, and others. Experiment with the Crural Nerve of Frog.In this experiment, one of the first by which Galvani was enabled to lay the foundation of that branch of electrical science now very commonly bearing his name, of the two metals employed one was made to touch the nerve of the frog's leg, the other at the same time the muscle; and in the directions for repeating the experiment, this is the arrangement usually laid down as requisite. If, however, the upper end of the nerve be dissected out from the thigh, and the metals be so placed that both shall be in contact at one of their extremities with this part, so that the current shall pass through the nerve alone, the muscular contraction and movement of the leg are equally great. The experiment in this form is conveniently performed by winding the sepa- M. Ruhmkorff, of Paris, was the first to prorated or free end of the nerve around one wire duce an actual combination or machine repreof a galvanic cell or element, and then touch-senting and taking advantage of these prining with the other wire any other point in the exposed nerve, so as to pass the current through the intervening portion. If the second wire touch the muscle, this serves as a conductor, and the contractions follow of course; but the preceding experiment appears to show that the effect is due in reality to passage of the current along a portion of the nerve. Electrical Phenomena of Vesuvius.-M. L. Palmieri first observed at the distance of a few hundred yards the flashes of volcanic lightning from a new crater of Vesuvius, at Torre del Greco. These flashes appeared always to originate in large globes of smoke, and they were followed by explosions not louder than the reports of pistols. Afterward, from the observatory he noticed similar flashes between smoke and cinder masses below and bodies of aqueous vapor above these; but very seldom between the smoke masses and the earth beneath. At each violent projection of smoke, his instruments indicated a strong tension of positive electricity; and when this reached a certain force, lightning and thunder occurred. If the electric discharge occurred in the direction of the zenith of the place, a sudden increase of ciples. This machine, known as Ruhmkorff's induction coil, consisted essentially of an inner helix of shorter and larger copper wire transmitting a current from a galvanic battery, with the addition of an interruptor to break the current at regular intervals, this helix being surrounded by and insulated from a second of finer wire and much longer, having at one end the condensing plates, and the extremities of which constituted the poles of the secondary current. With his arrangement the longest spark obtained did not quite equal one inch in length. Mr. Hearder, in 1857, improved the apparatus by more carefully insulating the helices, and obtained sparks of 3, and subsequently of 6 or 7 inches. Mr. E. S. Ritchie, of Boston, Mass., desiring in the same year to produce the induction coil and of increased power, found it impossible to construct it in the ordinary manner and yet free from liability of the breaking through of the spark from one coil to the other-a casualty that at once destroyed the action of the machine. His experiments led him to adopt an entirely new plan of winding the exterior coil, consisting finally in winding this wire in planes perpendicular to the axis of the helices, alternately running from the inner to the outer and from the outer to the inner diameters of the outer helix, and very carefully insulating not only between these strata but also between the inner and the outer helix. By these means he had in July of the year named produced an instrument giving sparks of 9 to 12 inches in length. Meanwhile, M. Ruhmkorff's best improved instruments had failed to give sparks of more than 3 or 4 inches in length. In the summer of 1858, Prof. R. S. MacCulloh, of Columbia College, N. Y., having secured for that institution one of these coils which, with a battery of only 4 Bunsen's cells, gave a spark 12 inches in length, ordered also one of Ruhmkorff's for which the French Academy had just awarded him a prize, and informed him of the power of Ritchie's machine, as also of the readiness professed by the latter maker to surpass the power of any instrument that might be so furnished. Receiving in the mean time no instrument from Paris, Prof. MacCulloh, in May, 1859, while on a tour in Europe, visited M. Ruhmkorff, who expressed an unwillingness to produce an instrument upon the conditions named, but showed one which he had attempted, and which had destroyed itself by the breaking of the spark through the insulation. Prof. MacCulloh, supposing that Ruhmkorff would be glad to compare Ritchie's instruments with his own and those of Hearder, and that he would of course accord due credit for what was original in the first named, presented him with one of these giving sparks of 7 inches. This M. Ruhmkorff dissected, for the purpose of examining its construction. About the same time, Prof. MacCulloh ordered of Ritchie the most powerful coil he could make, to be sent to Paris. Being received in November, this instrument and its performance were by him exhibited before Jacobi, Foucault, Duboscq, Jamin, Désains, Froment, and others distinguished in electrical or general physical science, as well as before the students of the Ecole de Médecine, and several professors of the Polytechnic School. M. Ruhmkorff, meantime, had a long-unfulfilled contract for a powerful coil for the last named school; and M. Jamin expressed himself in favor, in case such instrument should not be delivered by the close of the term of contract (March, 1860), of procuring one of Mr. Ritchie's instruments. In March, however, Ruhmkorff delivered to the school an instrument of his construction; and Prof. MacCulloh, on seeing this coil in May, was informed by M. Jamin that it was wound in portions perpendicular to the axis (Ritchie's system), and that it gave sparks of about the same length as the most powerful instrument of the latter, namely, 13 to 16 inches. M. Ruhmkorff showed to Prof. MacCulloh in June another instrument of like power, and of which he declared the construction to be similar. These facts are chiefly drawn from an account furnished to Mr. Ritchie for publication, by Prof. MacCulloh, since his return. The French scientific writers and journals, however, seem uniformly to ignore Ruhmkorff's indebtedness to Mr. Ritchie for an improvement which has fully tripled the power of the machine over that of any constructed by the previous methods; and they unite in awarding to the Parisian maker the entire credit of the invention of another. The Abbé Moigno, editor of the Cosmos, relates witnessing about the beginning of 1862 an experiment with one of Ruhmkorff's coils, which gave a spark 18 inches long, and pierced glass of two inches thickness. (See Mechan. Effects, &c., previous.) Conducting Power of Pure and Alloyed Copper.-Matthiessen and Holtzmann have presented before the Royal Society a paper on the effect of the presence of metals and metalloids upon the electric conducting power of pure copper. The variations in conductivity of copper wires as found by different experimenters, must depend in part on differences of quality and purity of the wires experimented with, and in part, at least, also on differences in temperature. Thus, taking the conducting power of pure silver as 100, the following are the measures for copper as found by the physicists named: Becquerel.. The temperatures at which the determinations were made are given only in the cases of Becquerel, Lenz, and Arndtsen, namely, 32°F. Matthiessen and Holzmann prepared pure cop, per, both by a method involving precipitation with sulphuretted hydrogen from the purest commercial sulphate of copper, and also by precipitating the metal galvano-plastically by a very weak current from the same compound. The conductivity of a hard-drawn silver wire being taken as 100, the mean of 12 determinations of hard-drawn wires from the copper so obtained gave for this metal 93.08, at 18.9° C. With similar wires annealed, there was a gain of 2.5 per cent., the mean in this case being 95.58. Copper fused in the air is probably always contaminated in degree with oxygen which it absorbs, producing some quantity of the suboxide; and the presence of this impurity was found always to reduce the conducting power, and in some cases to as low as from 69 to 73 in the scale. The experimenters could not induce the taking up by copper of more than .05 per cent. of carbon; but even this reduced the conduction to 74.91, at 18.3° C. Phosphorus, sulphur, selenium, and tellurium all very considerably reduced the conducting power of copper into which they entered as impurities; and arsenic in a still more remarkable degree-5.4 per cent. of arsenic giving a mean conducting power of only 6.18, at 16.8° C.; and 2.8 per cent., of 13.14, at 19.1° C. Of all the metallic impurities tin and iron most sensibly lowered the conducting power, the former, in amount |