existence of a nervous fluid, which, in the minds of nine-tenths of the masses, experiment had demonstrated beyond the shadow of a doubt.

But there were still some who doubted. Volta, the author of the Voltaic Pile, was not of the number who gave in their adhesion to a doctrine so preposterous. He visited Galvani, examined closely into the outward merits of his discovery, and returned to Pavia, where he shut himself up, and proceeded to analyze the scientific problem which had been propounded to him. He ascertained, at length, that the agitation of a nerve or muscle, when touched by two pieces of different metals, was greater than when touched by one; and, consequently, that instead of there being a nervous fluid resident in the organism, the electric property was confined alone to the metals. He had now overcome the difficult part of his task. His next step was to construct an apparatus, which should not only accumulate, but render continuous, the power that had puzzled Galvani, and which the latter had, without due investigation, at once ascribed to be a resident property of the nerves.

Volta's discovery was accepted as the true theory. The sydamic property was known to exist in contradistinction to the statical property, and all philosophy had to do, was to make that distinction by mechanical agency. Oersted, the Dane, was the man for the emergency. Ritter, of Munich, had already shown that metal could be magnetized by the Voltaic battery; but Oersted proved the existence of more remarkable phenomena relative to the action of the magnetic needle. He demonstrated how that, by the meeting of two electric currents, a new development of power ensues, which attracts or repels the needle of the North Pole, as it may be positive or negative, and that the direction of this power is not in a right, but in a spiral direction. Experience has confirmed the correctness of this view. Ampère, who was contemporary with Oersted, co-operated in shedding light upon the science. He simplified Oersted's system, and gave to it a more practical character. Ampère was in turn aided by M. Arago, who ascertained that, by plunging the wires of a battery into steel filings, the latter adhered to the wires so long as the electric current remained complete. If a wire could thus be magnetized at will, why, he argued, could not huge bars of iron? and acting on the suggestion, he caused a number of magnets to be forged, varying in size, which he tested, and satisfied himself that the opinion he had formed was well founded, in both principle and practice. Thus, we perceive, cloud after cloud was dispelled, until at length the auspicious light was to dawn upon the intellect.

But let us hurry on, and overtake those who have profited by Oersted's discovery, as simplified by Ampère. It is now 1811.

Soëmmering, of Munich, had, meanwhile, endeavored to apply voltaic electricity to telegraphy. His scheme was much the same as Le Sage's, that is, it comprehended as many wires as there are letters in the German alphabet, with the addition of numerals, from 0 to 9, all of which terminated in 35 golden points, in a vessel partially filled with water. Decomposition of the fluid took place when the fluid passed from the pile, and a bubble of oxygen or hydrogen gas appeared at the letter or numeral to which attention was desired. To this contrivance Schweigger added an alarm wire, by which signals by the operators were conveyed. He likewise proposed a reduction of wires to two; demonstrating the superior advantages of a less number than 35.

The deflection of the magnetic needle next became the subject of learned disquisition and eager research. The magnetic current, when passed along the line to any great distance, was found to be incapable of producing any well-defined movement, and Schweigger set about remedying this defect. He produced in time his multiplier; and the main drawback was rectified. This instrument deserves to be described. The principle on which it is constructed is, "that a current returning upon itself, acts in all its parts, and causes a powerful deviation of the mag netic needle placed with it;" and a "conducting wire, twisted upon itself, and forming a hundred turns, will, when traversed by the same current, produce an effect a hundred times greater than a wire with a single turn; provided always that the electric fluid pass through the circumlocutions of the wire without passing latterly from one contour to another." "This," adds the description, "is a condition easy to fulfil. To make a multiplier, you take a silver or copper wire of any length or size, closely enveloped in thick thread, and wind it round a small frame, within which the needle is suspended on a pivot, and leaving a few inches free at each extremity. These are called the two wires of the multiplier, and when in work, the current enters by one end, and passes off at the other."

We perceive that genius was rapidly accumulating all the practical elements of the synamic electro-telegraph. One more discovery would complete the triumph-that was, thermo-elec tricity, and science and enterprise soon conquered the sole remaining difficulty. Seebeck, of Berlin, stood forth, and successfully contended for the prize. He rightfully claimed the authorship of the theory, though Becquerel and Daniell improved and practically adapted it. Becquerel had shown, in carrying out the theory propagated by Volta, "that a pile might be constructed with a constant though feeble current," and it was of the first importance to find a stronger power. The pile was removed by Daniell, and substituted by batteries of various

forms. The zinc was plunged in a solution of chloride of sodium, and the copper in a solution of the sulphate of copper. The products of decomposition were ingeniously disposed of and the loss of power admirably guarded against, so that the action maintained its full force for a considerable duration of time. We have now all the elements of the electro-magnetic telegraph before us. Who, among the philosophers of the age, is it that comes forward and combines them? Morse, the American. Franklin, the American, had long before demonstrated the identity of electricity with lightning. It remained for Morse to group the combined wisdom of two ages in one grand and practical test, and to exhibit to mankind the novelty of lightning doing obeisance to every impulse of the human will. All im provements that have since been made, either by Professor Morse or his agents; by House and Bain of the United States; by Wheatstone and Smee of England; by Steinheil of Munich; by Voorsselman of Derenter; by Baron Schilling of Russia; by Puninge of France, and others, are all new adaptations or modifications of the same principle. But Professor Morse stands alone as the discoverer and the illustrious founder.

The battery, or generating power, is a simple apparatus. Let us imagine ourselves standing by the side of a wooden trough, which is divided off into twenty or forty cells, according to the power required. The partition walls are commonly of slate; they should always be of an incorrosible substance. Two plates of metal, one of zinc and the other of copper, laid alternately, are placed in each cell, in such a manner that all the plates of one kind face together towards one end of the trough; and those of the other face together on the opposite end of the trough. A ribbon of copper unites each pair of plates in the centre of the upper edges," forming, as it were, so many cur ved handles, by which they can be lifted in or out. As soon, then, as the remaining vacant space in each cell is filled with an acidulated fluid, the action commences; the acid begins to act upon the zine by dissolving it; the water contained in the solution is decomposed, and hydrogen is thrown off from the surface of the copper plates; while, by a combination of oxygen, oxide of zinc is formed, and this, dissolving in the acid-which is commonly sulphuric-sulphate of zinc is produced. These effects are the consequence of the general law established in relation to voltaic electricity, that by the contact of dissimilar metallic bodies, a partial transfer of the electric fluid from one to the other invariably takes place."" A "positive current is genera ted at the zinc, and passes to the copper through the intervening fluid in all the series of cells, and continues to flow as long as contact is maintained between the wires which depart from

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either end, whatever be their length." The cells of telegraph batteries are sometimes filled with well-washed sand, instead of a fluid; and this sand undergoes moistening by pouring in dilute sulphuric acid, which prevents a needless waste of the plates, while their full power is undiminished. The zinc is specially liable to oxydation and dissolution, to guard against which, it is only necessary to dip the plates frequently into a vessel of mercury. Persons who use the Leyden jar in their families, are well aware that their silver coating thus obtained prevents the wasteful effervescence that would otherwise ensue. The earth itself has been made to furnish a supply of the electric force, by a pair of zinc and copper plates being buried in a damp or wet subsoil. When saturated with water, the ground represents the sand, saturated with acid water, in the ordinary battery. A current of low intensity is thus obtained, notwithstanding that miles may intervene between the deposits of the plates. The earth acts as the return wire to any given number of wires, without in the least affecting the regularity of the action of any of them. The battery universally adopted in this country is that by Grove, "of cups of zinc, with strips of platinum in an earthenware or porcelain cup, which cup is filled with nitric acid, which is placed inside the zinc cup, in a tumbler filled with dilute sulphuric acid. The main battery on a line (from 30 to 50 cups) requires renewing only once in every two weeks, and daily in local batteries of two or three cups." Grove's battery, besides being the most consistent and economic, is the most powerful in use.

From the battery, which is kept in a remote and secure place,' we proceed to the operating room. Here the battery wires meet the telegraph wires in what is called the electro-magnetic machine. This apparatus externally resembles the works of a mantel-clock; but their operations, how similar, and yet how different! One computes, the other commutes, time. To describe the electro-magnetic machine is a difficult task. We have presented to us, for our inspection, manipulators, hieroglyphical characters on circular plates or planes, or rollers through which a strip of puncturated white paper is passing, and wheels innumerable, and a complication of other co-operating agents; but to the uninitiated the whole is a perplexing mystery. We perceive externally two needles, which are the tongues of the instrument, and the action of these is the language of the machine. The operator, with a message in writing before him, places his finger on a lever, and by compressing and relaxing this, the medium of correspondence is established. Within the machine are placed other needles to correspond with the external tongues, and are so situated that the South Pole of one and the North Pole of the other are in the same position, by which means the influence of the fluid is neutralized, or, rather, the action of the

magnetism upon them. They are kept in a perpendicular position, and are obedient to the slightest impulse from the battery. The inner needle is suspended within a multiplier, which intensifies the power of the electric current at this spot, and which deflects the needle to either side by the outward movement of the handle or lever, which opens or closes the electro-magnetic circuit. The secret of working the apparatus is easily acquired. The art, indeed, in many of the rural districts, is principally in the hands of women; and thousands, by this discovery of science, now earn livelihoods at the electro-machine, who otherwise might be, or have remained, drudges in less intellectual employments.

Art. IV. MAGNETIC BATTERY FOR TELEGRAPHING.

NEW INVENTION OF MR. CARPENTER-MAGNETIC BATTERY PROPOSED AND CLAIMED AS SUPERIOR TO THE GALVANIC BATTERY.

WE have, on several occasions, spoken of the necessity for improving the present battery arrangements of the electric telegraphs of America, and have expressed the hope that, at an early day, a mode would be devised to generate electric power, consummating the purposes at reduced expense.

Various plans have been suggested, and many experiments have been made, and some have apparently proved successful. Whether or not they would answer the purposes of telegraphing we are unable to say, as the question can only be settled by actual application in the premises.

We give below a very interesting communication from Mr. Calvin Carpenter, of Rhode Island. We have seen his battery, and it seemed to fully sustain all the gentleman claims for it. It is worthy of trial; and if it does answer, the economy in its use will be very great. We hope the subject will be well considered, and the merits of this, as well as all other plans, have a fair and practical examination.

The plan of Mr. Carpenter, to have batteries at leading points to charge a range of lines, of course we consider wholly impracticable. His limited acquaintance with the management and operation of lines deprives him of a proper basis of calcula tion. It is not economy for lines to operate in long circuits; and the plan proposed would not be economy. But this is not a material point in the consideration of the subject in detail. If these batteries do answer, it would be a great saving to have them at every office. Once supplied, there will be no more cost.

While we wish the subject of batteries to be fully examined, we do not recommend the abolishment of those existing, until there is a certainty of success in those which may be substituted. Too much care cannot be taken as to proper electric force;