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friction of the journals carrying the arrangement. If the coil completes the electric circuit within itself, so that there is no external resistance, then the total heat will be developed therein. If the circuit is made complete by a conductor, then the heat will be divided between the coil and conductor in proportion to their respective resistances. If this conductor be the coils of an electro-motor, the heat due to it can be utilized as work, less loss by conversion.

We have now the general requirement laid down, so we will proceed to plan and construct a theoretical machine to suit the requirements of 1000 horse-power, to be transmitted, if possible, through a rod of copper, thirty miles in length and three inches in diameter. As resistance of wire of same diameter is in direct proportion to its length, and as we have seen that 6046.5 feet of copper wire, one-quarter inch in diameter, has a resistance of 1 ohm, so 30 miles, or 158,400 feet of one-quarter inch wire, has 26 ohms resistance. But, as it also decreases in proportion to the square of the diameters, we figure in the three-inch rod a resistance of .18 ohm, if of pure copper, at a temperature of 60° Fahr.

The energy of 1000 horse-power is measured at 33,000,000 footpounds per minute, and that of one weber current equals 4673 footpounds in 6338 seconds, or 44.24 foot-pounds per minute. So it will require 746,000 'webers current, or their equivalent in energy, to utilize 1000 horse-power as electricity for dynamic purposes.

We may, therefore, use electromotive force of 1000 volts, resistance of 1.34 ohms, and a current of 746 webers; thus

1000 E

1.34 R

746 C.

In other words, the dynamic equivalent of 746,000 webers may be had by multiplying the electromotive force 1000 by the current 746.

It has been found that a discharge of the magnetism of a soft iron core induces a current in the coil surrounding it, possessing electromotive force of one volt for about each twenty-five feet of coil. The quantity or current comes from the strength of the magnetism and number of discharges. For 1000 volts electromotive force we will take 25,000 feet in length of copper wire or strips, weighing 1.2 pounds per foot length, or in all 30,000 pounds. This will have a resistance of .66 ohm. It should be wound upon a core of iron weighing 10,000 pounds. This core and coil, constituting what is called an armature, must be revolved between the poles of an electro-magnet having such an attraction for the armature as to call for the expenditure of 1000 horse-power in revolving it. Such a magnet will

weigh, probably, 60,000 pounds, and have a like weight of copper in its coils. It should be excited or magnetized by a smaller armature revolved between the poles of a smaller magnet, with an expenditure of, say, 100 horse-power. This is necessary, because, if the coil of the magnet is part of the main circuit, the resistance will be much increased.

The electromotor receiving the current of electricity must have at least the same length of copper in its coils; and as the resistance of the coils (when the machine in motion is exerting its greatest power) is double that which they have at rest, and as it is necessary from our other fixed resistances to make the resistance of the machine .50 ohm, we make the weight of copper coils per foot 3.17 pounds, a total of 79,200 pounds, with a weight of iron about 70,000 pounds.

The cost of this apparatus will be as follows:

3,000 lb. copper, 30c. per lb.,

Total for machine,

Conductor: 158,400 feet copper rod at 27 lb per foot, 4,356,000 lb.,

Exciting magnet and armature:

$3,500

Large magnet, 60,000 lb. iron, including work thereon, 10c. per lb., 60,000 lb. copper, 30c. per lb., .

6,000

18,000

Armature: 10,000 lb. iron, and work thereon, 10c. per lb.,

1,000

9,000

Brass bearings, brushes, etc.,

2,500

$40,000

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The energy of 1000 horse-power expended on the machine generating the electric current is distributed throughout the circuit in proportion to the special resistances of the several parts. The armature, having a resistance of .66 ohm, absorbs 66-134 or 492.5 horsepower; the conductor 18-134 or 134.3 horse-power; the motor 50-134 or 373.2 horse-power. This last amount is all that can be utilized with this arrangement, even if there is no loss. We may make our electric machine and the motor larger, or place two of them, making the resistances of them one-half as much, but not with any increase of utilizable power, as the resistance of the conductor remains the

same.

Let us consider a resistance of .33 ohm for machine, .18 ohm for conductor, and .25 ohm for motor, and we have 33-76 or 434 horsepower for machine, 18-76 or 237 horse-power for conductor, and 25-76 or 329 horse-power for motor. This is less available power than before. The resistance of the earth returning the current we may count as nothing. Under no circumstances can we utilize the full power expended.

If we decrease the resistance of the machine to .33 ohm, and increase that of the motor to .83, keeping total resistance the same, we will gain. Then the machine will absorb 33-134 or 246.2 horse-power; the conductor 18-134 or 134.3 horse-power; and the motor 619.5 horse-power. With a larger conductor or shorter distance, this proportion may be increased.

There are various sources of loss, especially with electricity of such electromotive force and tension. I have no doubt that at least 50 per cent. of the energy expended on a magneto-electric or dynamoelectric machine at a waterfall may be used at a distance by an electro-magnetic motor as mechanical power.

The amount of heat developed throughout the entire circuit will be equivalent to that from the combustion of 200 lbs. of coal per hour, or 42.746 heat units per minute. That proportion due to the armature, having resistance of .33 ohm, is sufficient to raise its temperature one degree Centigrade per minute. Of course, then, some arrangement for cooling by water must be applied. What the effect of a discharge of a portion even of this current, with its high tension, through the body of a man would be, I leave you to imagine.

COPPER BY ELECTRICITY.

BY N. S. KEITH, NEW YORK CITY.

(Read at the Amenia, Meeting, October, 1877.)

SOME time ago, a firm engaged largely in the manufacture of copper sulphate, applied to me for information as to the practicability of obtaining the copper from their mother liquors by means of electricity; having reference, more especially, to obtaining the electric current from some magneto-electric or dynamo-electric machine.

The mother liquors were the result of several solutions of commercial scrap copper, containing impurities, the quantity of which

in the liquors had increased by the operations until too large to allow the formation of pure, or even merchantable copper sulphate. There were silver, nickel, tin, zinc, antimony, and iron sulphates in solution, besides enough copper sulphate to represent 4 per cent. of the total weight of solution as metallic copper. The question was: "Can we obtain this copper in a cheap, practicable, and expeditious way by the agency of electricity?"

They had tried experiments so far as to determine to their own satisfaction the previously known fact, that the copper could be deposited by electricity; requiring, however, to do so, three cells of a gravity battery, say an electromotive force of three volts. A less electromotive force would not accomplish it.

Knowing, then, this fact, it was nècessary to employ a machine to produce electricity of at least that amount of electromotive force, and of a size to offer a small resistance to the electric current generated, and depositing vessels large enough to accommodate the amount of liquor, and large enough electrodes to make the resistance low; so that the combined resistances of machine, conductors, electrodes, and liquors were low enough to allow sufficient current to flow, all in obedience to Ohm's law, which is formulated thus:

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Further, electrotypers carry on their art of depositing copper electrically by the use of batteries having, say, half a volt electromotive force. Why, then, is it necessary to use three volts-nearly six times as much, to deposit copper in this case?

Electrotypers use a copper anode which is dissolved, and by its solution as much force is set free in the electric circuit as is absorbed by the deposition of a like amount of copper on the cathode. So, as no force is set up against the electric force, the weakest battery is capable of depositing some copper. The practical point with the electrotyper is a speed of deposit which gives him a coherent, reguline shell of copper in the shortest possible time, with the least expenditure of force. As that force for his use exists in zinc and acid, or in the mechanical motion applied to a dynamo-electric machine, he uses one or the other, according to the extent of his information or the condition of his pocket. The machine would undoubtedly give him equal current for less than one-tenth of the cost by use of zine and sulphuric acid. The consumption of an electric equivalent (65 grains) of zinc in a single Smee cell, will give a deposit in a

copper-depositing cell, with soluble anode, of an equivalent (63.5 grains) of copper. If we substitute an insoluble anode, to completely deposit the copper, we must place six Smee cells in series, in order to have an electromotive force at our command of three volts; consequently we will use 65 grains of zinc in each cell, or 390 grains in all, to get a deposit of 63.5 grains of copper. Thus, 325 grains of zinc are used in decomposing water, and setting free oxygen as gas at the insoluble anode-so much energy lost, so far as the practical result is concerned. Other cells, having greater electromotive force, like Daniell's, Grove's, Bunsen's, and the gravity battery, may be used with less waste of zinc. A single cell of the gravity battery employed, would give a deposit of copper to the electrotyper by the expenditure of equivalent of zinc for equivalent of copper.

The electromotive force of a battery-cell is the remainder after subtracting the force of the negative element from the force of the positive element. Thus in a Daniell cell the force of the union of 32.6 grains of zinc with SO, is 10,503 foot pounds; from that take the force of the union of equivalent copper with SO, 5878 foot pounds, and we have 4625 foot pounds, available force of a Daniell cell. Against that we have no force set up in the electrotyper's cell, since as much force is given by the solution of copper as is absorbed by its reduction.

In an arrangement for the complete deposition of copper from its sulphate solution, we have a counter-electromotive force equal to the difference between the forces of copper cathode and a platinum or carbon anode, and the force absorbed by the deposited copper at the cathode and the liberated oxygen at anode.

After these facts were considered, the question of choice of anode arose. If we use a copper one, we might go on indefinitely depositing copper without exhausting the solution, or liquor; if we use an anode of a metal electro-positive to copper, like zinc or iron, as soon as it is immersed in the solution it is immediately covered with a fine powder of metallic copper in the well-known way; so we might as well use those metals directly without the electricity. If we use copper matte for an anode, we will still be taking copper into the liquor as well as iron, etc. Now for the insoluble anodes-elements electro-negative to copper. Lead is cheap, but it soon covers with a thin film of insoluble lead sulphate, which offers a great resistance

to the passage of the current. Carbon plates, made by causing gascoal graphite to cohere, conduct the current well, but under the action

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