Chapter IX: Electricity (2)

By inserting into the mass of a copper _lode_, or vein, in situ, a metallic wire, which shall be connected with a measurer of galvanic action, a wire also from the instrument being brought into contact with another _lode_, an immediate effect is generally produced, showing that a current is traversing through the wires from one _lode_ to the other, and completing the circulation probably over the dark face of the rock in which the fissures forming the mineral veins exist.[158] The currents thus detected are often sufficiently active to deflect a magnetic needle powerfully, to produce, slowly, electro-chemical decomposition, and to render a bar of iron magnetic. These currents must not be confounded with the great electrical movements around the earth. They are only to be detected in those mineral formations in which there is evidence of chemical action going on, and, the greater the amount of this chemical operation, the more energetic are the electrical currents.[159] We have, however, very good evidence that these local currents have, of themselves, many peculiar influences. It not unfrequently happens that owing to some great disturbance of the crust of the earth, a mineral vein is dislocated, and one part either sinks below, or is lifted above its original position; the fissures formed between the two being usually filled in with clay or with crystalline masses of more recent formation than the fissure itself. It is frequently found that these “_cross courses_,” as they are called in mining language, contain ores of a different character from those which constitute the mineral vein; for instance, in them nickel, cobalt, and silver are not unfrequently discovered. When these metals are so found, they almost invariably occur between the ends of the dislocated lode, and often take a curvilinear direction, as if they were deposited along a line of electrical force.[160]

In the laboratory such an arrangement has been imitated, and in a mass of clay fixed between the galvanic plates, after a short period a distinct formation of a mineral vein has taken place.[161] By the action, too, of weak electrical currents, Becquerel, Crosse, and others, have been successful in imitating nature so far as to produce crystals of quartz and other minerals. In addition to this evidence, in support of the electrical theory of the origin of mineral veins, it can be experimentally shown that a schistose structure may be given to clays and sandstone by voltaic action.[162]

There is often a very remarkable regularity in the direction of mineral veins: throughout Cornwall, for instance, they most commonly have a bearing from the E. of N. to the W. of S. It has hence been inferred that they observe some relation to the magnetic poles of the earth. However this may be, it is certain that the ore in any lodes which are in a direction at right angles, or nearly so, to this main line, differs in character from that found in these, so called, east and west lobes.[163]

The sources of chemical action in the earth are numerous. Water percolating through the soil, and finding its way to great depths through fissures in the rocks, carries with it oxygen and various salts in solution. Water again rising from below, whether infiltrated from the ocean or derived from other sources, is usually of a high temperature, and it always contains a large quantity of saline matter.[164] By these causes alone chemical action must be set up. Chemical change cannot take place without a development of electricity: and it has been proved that the quantity of electricity required for the production of any change is equal to that contained in the substances undergoing such change. Thus a constant activity is maintained within the caverns of the rock by the agency of the chemical and electrical elements, and mutations on a scale of great grandeur are constantly taking place under some directive force.

The mysterious gnome, labouring--ever labouring--in the formation of metals, and the mischievous Cobalus of the mine, are the poor creations of superstition. A vague fear is spread amongst great masses of mankind relative to the condition of the dark recesses of the earth; a certain unacknowledged awe is experienced by many on entering a cavern, or descending a mine: not the natural fear arising from the peculiarity of the situation, but the result of a superstitious dread, the effect of a depraved education, by which they have been taught to refer everything a little beyond their immediate comprehension to supernatural causes. The spirit of demon worship, as well as that of hero worship, has passed from the early ages down to the present; and under its influence the genii of the East and the demons of the West have preserved their traditionary powers.

Fiction has employed itself with the utmost license in giving glowing pictures of treasures hidden in the earth’s recesses. The caverns of Chilminar, the cave of Aladdin, the abodes of the spirits of the Hartz, and the dwellings of the fairies of England, are gem-bespangled and gold-glistening vaults, to which man has never reached. The pictures are pleasing; but although they have the elements of poetry in them, and delight the young mind, they want the sterling character of scientific truth; and the wonderful researches of the plodding mineralogist have developed more beauty in the caverns of the dark rock than ever fancy painted in her happiest moments.

In all probability the action of the sun’s rays upon the earth’s surface, producing a constantly varying difference of temperature, and also the temperature which has been observed as existing at great depths, give rise to thermo-electrical currents, which may play an important part in the results thus briefly described.

In connection with these great natural operations, explaining them, and being also, to some extent, explained by them, we have the very beautiful application of electricity to the deposition of metals, called the Electrotype.

Applying the views we have adopted to this beautiful discovery,[165] the whole process by which these metallic deposits are produced will be yet more clearly understood. By the agency of the electric fluid, liberated in the galvanic battery, a disturbance of the electricity of the solution of copper, silver, or gold, is produced, and the metal is deposited; but, instead of allowing the acid in combination to escape, it has presented to it some of the same metal as that revived, and, consequently, it combines with it, and this compound, being dissolved, maintains the strength of the solution.[166] A system of revival, or decomposition, is carried on at one pole, and one of abrasion, or more correctly speaking, of composition and solution, at the other. By taking advantage of this very extraordinary power of electricity, we now form vessels for ornament or use, we gild or silver all kinds of utensils, and give the imperishability of metal to the most delicate productions of nature--her fruits, her flowers, and her insects;--and over the finest labours of the loom we may throw coatings of gold or silver to add to their elegance and durability. Nor need we employ the somewhat complex arrangement of the battery: we may take the steel magnet, and, by mechanically disturbing the electricity it contains, we can produce a current through copper wires, which may be used, and is extensively employed, for gilding and silvering.[167] The earth itself may be made the battery, and, by connecting wires with its mineral deposits, currents of electricity have been secured, and used for the production of electrotype deposit.[168]

The electrotype is but one of the applications of electricity to the uses of man. This agent has been employed as the carrier of thought; and with infinite rapidity, messages of importance, communications involving life, and intelligences outstripping the speed of coward crime, have been communicated. There will be no difficulty in understanding the principle of this, although many of the nice mechanical arrangements, to ensure precision, are of a somewhat elaborate character. The entire action depends on the deflection of a compass-needle by the passage of an electric current along its length. If at a given point we place a galvanic battery, and at twenty or one hundred miles distance from it a compass-needle, between a wire brought from, and another returning to the battery, the needle will remain true to its polar direction so long as the wires are unexcited; but the moment connection is made, and the circuit is complete, the electricity of the whole extent of wire is disturbed, and the needle is thrown at right angles to the direction of the current. Provided a connection between two points can be secured, however remote they are from each other, we thus, almost instantaneously, convey any intelligence. The effects of an electric current would appear at a distance of 576,000 miles in a second of time; and to that distance, and with that speed, it is possible, by Professor Wheatstone’s beautiful arrangements, to convey whispers of love or messages of destruction.

The enchanted horse of the Arabian magician, the magic carpet of the German sorcerer, were poor contrivances, compared with the copper wires of the electrician, by which all the difficulties of time and the barriers of space appear to be overcome. In the Scandinavian mythology we find certain spiritual powers of evil enabled to pass with imperceptible speed from one remote point to another, sowing the seeds of a common ruin amongst mankind. Such is the morbid creation of a wild yet highly endowed imagination. The spirit of evil diffuses itself in a remarkable manner, and, indeed, we might almost assign to it the power of ubiquity; but in reality its advance is progressive, and time enters as an element into any calculation on its diffusion. Electricity is instantaneous in action; as a spirit of peace and good-will it can overtake the spirit of evil, and divert it from its designs. May we not hope that the electrical telegraph, making, as it must do, the whole of the civilized world enter into a communion of thought, and, through thought, of feeling with each other, will bind us up in one common brotherhood, and that, instead of misunderstanding and of misinterpreting the desires and the designs of each other, we shall learn to know that such things as “natural enemies” do not exist? To hope to break down the great barrier of language is perhaps too much; but assuredly we may hope that, as we must do when closer and more intimate relations are secured by the aids of science, the barrier of prejudice may be razed to the ground, and not one stone left to stand upon another? Our contentions, our sanguinary wars, consecrated to history by the baptism of blood, have in every, or in nearly every, instance sprung from the force of prejudice, or the mistakes of politicians, whose minds were narrowed to the limits of a convention formed for perpetuating the reign of ignorance.

And can anything be more in accordance with the spirit of all that we revere as holy, than the idea that the elements employed by the All Infinite in the works of physical creation shall be made, even in the hands of man, the ministering angels to the great moral redemption of the world? Associate the distant nations of the earth, and they will find some common ground on which they may unite. Mortality compels a dependence; and there are charities which spring up alike in the breast of the savage and the civilized man, which will not be controlled by the cold usages of pride, but which, like all truths, though in a still small voice, speak more forcibly to the heart than errors can, and serve as links in the great chain which must bind mankind in a common brotherhood. “None are all evil,” and the best have much to learn of the amenities of life from him who yet lives in a “state of nature,” or rather from him whose sensualities have prevailed over his intellectual powers, but who still preserves many of the noblest instincts, to give them no higher term, which other races, proud of their intelligence, have thrown aside. Time and space have hitherto prevented the accomplishment of this; electricity and mechanics promise to subdue both; and we have every reason to hope those powers are destined to accelerate the union of the vast human family.

Electrical power has also been employed for the purpose of measuring time, and by its means a great number of clocks can be kept in a state of uniform correctness, which no other arrangement can effect. A battery being united with the chief clock, which is itself connected by wires with any number of clocks arranged at a distance from each other, has the current continually and regularly interrupted by the beating of the pendulum, which interruption is experienced by all the clocks included in the electric circuit; and, in accordance with this breaking and making contact, the indicators or hands move over the dial with a constantly uniform rate. Instead of a battery the earth itself has supplied the stream of electric fluid, with which the rate of its revolutions has been registered with the utmost fidelity.[169]

Electricity, which is now employed to register the march of time, rushes far in advance of the sage who walks with measured tread, watching the falling sands in the hour-glass.

The earth is spanned and the ocean pierced by the wires of the electric telegraph. Already, from the banks of the Thames to the shores of the Adriatic, our electric messenger will do our bidding. The telegraph is making its way through Italy, and it is dipping its wires in the Mediterranean, soon to reach the coast of Africa. They will then run along the African shores to Egypt and Turkey, and still onward until they unite with the telegraphs of India, of which three thousand miles are in progress. From Hindostan these wondrous wires will run from island to island in the Indian Archipelago, and thus connect Australia and New Zealand with Europe.

In a few years we may expect to have an instantaneous report in London of the extraordinary “nugget” discovered by some fortunate gold-digger; and the exile from his native land in the Islands of the South Pacific Ocean, may learn every hour, if he will, of the doings of his family and friends in some village home of England.

FOOTNOTES:

[136] _Traité de Physique_: M. Biot, vol. vii. Becquerel: Annales de Chimie, vol. xlvi.-xlix. Faraday’s _Experimental Researches in Electricity_, 2 vols., 1830-1844. _A Speculation touching Electric Conduction and the Nature of Matter_: by Michael Faraday, D.C.L., F.R.S.; Philosophical Magazine, vol. xxiv., 1836. _Objections to the theories severally of Franklin, Dufay, and Ampère, with an attempt to explain Electrical Phenomena by statical or undulatory polarization_: by Robert Hare, M.D., Emeritus Professor of Chemistry in the University of Pennsylvania.

[137] “A good piece of gutta percha will insulate as well as an equal piece of shell-lac, whether it be in the form of sheet, or rod, or filament; but being tough and flexible when cold, as well as soft when hot, it will serve better than shell-lac in many cases where the brittleness of the latter is an inconvenience. Thus it makes very good handles for carriers of electricity in experiments on induction; not being liable to fracture in the form of thin band or string, it makes an excellent insulating suspender; a piece of it in sheet makes a most convenient insulating basis for anything placed on it. It forms excellent insulating plugs for the stems of gold-leaf electrometers, when they pass through sheltering tubes, and larger plugs form good insulating feet for electrical arrangements; cylinders of it, half an inch or more in diameter, have great stiffness, and form excellent insulating pillars. In these and in other ways its power as an insulator may be useful.”--_On the use of Gutta Percha in Electrical Insulation_: by Dr. Faraday; Philosoph. Mag., March, 1848.

The following deductions have been given by Faraday, in his _Researches in Electricity_, a work of most extraordinary merit, being one of the most perfect examples of fine inductive philosophy which we possess in the English language:--

“All bodies conduct electricity in the same manner from metals to lacs and gases, but in very different degrees.

“Conducting power is in some bodies powerfully increased by heat, and in others diminished, yet without one perceiving any accompanying essential electrical difference, either in the bodies, or in the change occasioned by the electricity conducted.

“A numerous class of bodies insulating electricity of low intensity, when solid, conduct it very freely when fluid, and are then decomposed by it.

“But there are many fluid bodies which do not sensibly conduct electricity of this low intensity; there are some which conduct it and are not decomposed; nor is fluidity essential to decomposition.

“There are but two bodies (sulphuret of silver and fluoride of lead) which, insulating a voltaic current when solid, and conducting it when fluid, are not decomposed in the latter case.

“There is no strict electrical distinction of conduction which can as yet be drawn between bodies supposed to be elementary, and those known to be compounds.”

[138] Faraday’s _Speculation on the Nature of Matter_, already referred to.

[139] _Experimental Researches_: by Dr. Faraday. _Chemical Decomposition_, p. 151.

[140] Karsten; Poggendorff’s _Annalen_, vol. lvii.

[141] _Traité Expérimental de l’Électricité et du Magnétisme_: Becquerel, 1834, Priestley’s _Introduction to Electricity_. _On Electricity in Equilibrium_: Dr. Young’s Lectures.

[142] Faraday’s _Experimental Researches on Electricity_. This philosopher has shown, by the most conclusive experiments, “that the electricity which decomposes, and that which is evolved by the decomposition of, a certain quantity of matter, are alike. What an enormous quantity of electricity, therefore, is required for the decomposition of a single grain of water! We have already seen that it must be in quantity sufficient to sustain a platinum wire 1/104 of an inch in thickness, red hot, in contact with the air, for three minutes and three quarters. It would appear that 800,000 charges of a Leyden battery, charged by thirty turns of a very large and powerful plate machine, in full action--a quantity sufficient, if passed at once through the head of a rat or cat, to have killed it as by a flash of lightning--are necessary to supply electricity sufficient to decompose a single grain of water; or, if I am right, to equal the quantity of electricity which is naturally associated with the elements of that grain of water, endowing them with their mutual chemical affinity.”

[143] _Experimental Researches_: Faraday.

[144] The appearance of acid and alkaline matter, in water acted on by a current of electricity, at the opposite electrified metallic surfaces, was observed in the first chemical experiments made with the column of Volta--(see Nicholson’s Journal, vol. iv. p. 183, and vol. iv. p. 261, for Mr. Cruickshank’s Experiments; and Annales de Chimie, tom. xxxvii. p. 233, for those of M. Desormes): _On some Chemical Agencies in Electricity_: by Sir Humphry Davy.--Philosophical Transactions for 1807. The various theories of electro-chemical decomposition are carefully stated by Faraday, in his fifth series of _Experimental Researches on Electricity_, in which he thus states his own views:--“It appears to me that the effect is produced by an _internal corpuscular action_ exerted according to the direction of the electric current, and that it is due to a force either _superadded to_ or _giving direction to the ordinary chemical affinity_ of the bodies present. The body under decomposition may be considered as a mass of acting particles, all those which are included in the course of the electric current contributing to the final effect; and it is because the ordinary chemical affinity is relieved, weakened, or partly neutralized by the influence of the electric current in one direction parallel to the course of the latter, and strengthened or added to in the opposite direction, that the combining particles have a tendency to pass in opposite courses.”

[145] “This capital discovery (chemical decomposition of electricity) appears to have been made in the first instance by Messrs. Nicholson and Carlisle, who observed the decomposition of water so produced. It was speedily followed up by the still more important one of Berzelius and Hisinger, who ascertained it as a general law, that, in all the decompositions so effected, the acids and oxygen become transferred and accumulated around the positive, and hydrogen, metals, and alkalies around the negative, pole of a voltaic circuit; being transferred in an invisible, and, as it were, a latent or torpid state, by the action of the electric current, through considerable spaces, and even through large quantities of water or other liquids, again to reappear with all their properties at their appropriate resting-places.”--_Discourse on the Study of Natural Philosophy_: by Sir John Herschel, Bart., F.R.S.

[146] Numerous beautiful illustrations of this fact will be found in Becquerel’s _Traité Expérimental de l’Électricité et du Magnétisme_.

[147] See _Le Feu élémentaire_ of l’Abbé Nollet; Leçons de Physique, tom. vi. p. 252; _Du Pouvoir thermo-électrique_, by M. Becquerel--Annales de Chimie, vol. xli. p. 353; also a Memoir by Nobili, Bibliothèque Universelle, vol. xxxvii. p. 15; _Experimental Contributions towards the theory of Thermo-Electricity_ by Mr. J. Prideaux--Philosophical Magazine, vol. iii., Third Series; _On the Thermo-Magnetism of Homogeneous Bodies, with illustrative experiments_, by Mr. William Sturgeon--Philosophical Magazine, vol. x. p. 1-116, New Series. Botto made magnets and obtained chemical decomposition. Antinori produced the spark. Mr. Watkins heated a wire in Harris’s Thermo-Electrometer.

[148] A very ingenious application of the knowledge of this fact was suggested by Mr. Solly, by which the heat of a furnace could be constantly registered at a very considerable distance from it. See _Description of an Electric Thermometer_: by E. Solly, Jun., Esq. Philosophical Magazine, vol. xx. p. 391. New Series.

[149] Humboldt; _Personal Narrative_, Chap. xvii.--Annales de Chimie, vol. xiv. p. 15.

[150] _Experimental Researches on Electricity._ Series xv. Consult Sir Humphry Davy: _An Account of some Experiments on the Torpedo_.--Philosophical Transactions, 1829, p. 15. John Davy, M.D., F.R.S.: _An Account of some Experiments and Observations on the Torpedo_, ibid., 1832, p. 259; and the same author’s _Observations on the Torpedo, with an Account of some Additional Experiments on its Electricity_; and Matteucci, Bibliothèque Universelle, 1837, vol. xii. p. 174.

[151] _On Lightning Conductors_, by Sir William Snow Harris; _Observations on the Action of Lightning Conductors_, by W. Snow Harris, Esq., F.R.S.--London Electrical Society’s Transactions. Numerous valuable papers _On Electricity_, by Sir William Harris, will be found in the Philosophical Transactions.

[152] Adopting, to a certain extent, this view, Faraday, in his _Electrical Nomenclature_, proposed for the word pole to substitute _anode_ (ανω, _upwards_, and ὁδος, _a way_), the way which the sun rises; and _cathode_ (κατα, _downwards_, and ὁδος, _a way_), the way which the sun sets. The hypothesis belongs essentially to Ampère. _Objections to the Theories severally of Franklin, Dufay, and Ampère, with an Effort to Explain Electrical Phenomena by Statical or Undulatory Polarisation_, by Robert Hare, M.D., Pennsylvania, will well repay an attentive perusal.

[153] _Inquiry into the Laws of the Vital Functions._--Philosophical Transactions, 1815, 1822; _Some Observations relating to the Functions of Digestion_, ibid., 1829: _On the Powers on which the Functions of Life in the more perfect animals depend, and on the manner in which they are associated in the production of their more complicated results_, by A. P. W. Philip, M.D., F.R.S., L. and E.--The following extract from the last-quoted of Dr. Philip’s Memoirs, will give a general view of the conclusions of that eminent physiologist:--“With respect to the nature of the powers of the living animal which we have been considering, the sensorial and muscular powers, and the powers peculiar to living blood, we have found belong to the living animal alone, all their peculiar properties being the properties of life. The functions of life may be divided into two classes, those which are affected by the properties of this principle alone, and those, by far the most numerous class, which result from the co-operation of these properties with those of the principles which operate in inanimate nature. The nervous power we have found to be a modification of one of the latter principles, because it can exist in other textures than those to which it belongs in the living animal, and we can substitute for it one of those principles without disturbing the functions of life.

“Late discoveries have been gradually evincing how far more extensive than was supposed, even a few years ago, is the dominion of electricity. Magnetism, chemical affinity, and (I believe from the facts stated in the foregoing paper, it will be impossible to avoid the conclusion) the nervous influence, the leading power in the vital functions of the animal frame, properly so called, appear all of them to be modifications of this apparently universal agent; for I may add we have already some glimpses of its still more extensive dominion.”

Refer to Dr. Reid’s papers.

[154] _Electro-physiological Researches_: by Signor Carlo Matteucci; Phil. Trans. 1845, p. 293, and subsequent years.

[155] Electro-Biology: by Alfred Smee, Esq.

[156] _Observations of Electric Currents in Vegetable Structures_: by Golding Bird, Esq., F.L.S.; Magazine of Natural History, vol. x. p. 240. In this paper Dr. Bird remarks that his experiments lead to the conclusion that vegetables cannot become so charged with electricity as to afford a spark; that electrical currents of feeble tension are always circulating in vegetable tissues; and that electrical currents are developed during germination from chemical action.

[157] _On Mineral Veins_: by Robert Were Fox, Esq.; Fourth Report of the Royal Cornwall Polytechnic Society. _On the Electro-magnetic Properties of Metalliferous Veins in the mines of Cornwall_: by Robert W. Fox, Esq.; Phil. Trans. 1830, p. 399.

[158] _Experiments and Observations on the Electricity of Mineral Veins_: by Robert Hunt and John Phillips; Reports of the Royal Cornwall Polytechnic Society for 1841-42. _On the Electricity of Mineral Veins_: by Mr. John Arthur Phillips; Ibid., 1843.

[159] In the lead lodes of _Lagylas_ and _Frongoch_, electrical currents were detected by Mr. Fox, but none in those of _South Mold_ and _Milwr_, in Flintshire: Cornwall Geological Transactions, vol. iv. In the lead veins of _Coldberry_ and _Skeers_, in Teasdale, Durham, the currents detected were very feeble: Reports of the Bristol Association, 1838. Von Strombeck could detect no electric currents in the veins worked in the clay slate near Saint Goar, on the Rhine: Archiv. für Mineralogie, Geognosie, &c., von Dr. C. J. B Karsten, 1833. Professor Reich, however, obtained very decided results at _Frisch Glück_, _Neue Hoffnung_, _Gottlob_, and in other mineral veins in the mining districts of Saxony: Edinburgh New Philosophical Journal, vol. xxviii. 1839. The irregularities are all to be explained by the presence or absence of chemical excitation.

[160] This was remarkably the case at _Huel Sparnon_, near Redruth, where the cobalt was discovered between two portions of a dislocated lode; and the same was observed by Mr. Percival Johnson in a small mine worked for nickel, near St. Austell.

[161] _On the process used for obtaining artificial veins in clay_: by T. B. Jordan; Sixth Annual Report of the Royal Cornwall Polytechnic Society. See also my memoir, already referred to, in the Memoirs of the Geological Survey and Museum of Practical Geology, vol. i.

[162] See Becquerel, _Traité Experimental de l’Electricité, &c. Electrical Experiments on the formation of Artificial Crystals_: by Andrew Crosse, Esq.; British Association Reports, vol. v., 1836. The lamination of clay and other substances is described in my memoir referred to, Note p. 226.

[163] Report on the Geology of Cornwall, Devon, and West Somerset, by Sir Henry T. De la Beche: _Theoretical observations on the formation and filling of Mineral Veins and Common Faults_, p. 349.

[164] The following analyses of waters from deep mines were made by me in 1840, and, with many others, published in the Reports of the Royal Cornwall Polytechnic Society.

Consolidated Mines, Gwennap,
Cornwall. In 1,000 grains of water.
Muriate of soda 1·5
Sulphate of lime ·5
Sulphate of iron ·15
Sulphate of copper 1·25
Silica ·15
Alumina ·3
----
Total 3·7

United Mines, Gwennap.
Muriate of soda 1·10
Muriate of lime ·15
Sulphate of soda ·50
Sulphate of lime 1·5
Sulphate of iron ·75
Alumina ·5
Silica ·15
----
Total 4·65

Great St. George.
Muriate of soda 1·35
Sulphate of lime ·74
Carbonate of iron ·70
Alumina ·50
Carbonate of lime ·10
----
Total 3·4

[165] The discovery of the electrotype has been disputed, as all valuable discoveries are. Without, however, at all disparaging the merits of what had been done by Mr. Jordan, I am satisfied, after the most careful search, that the first person who really employed electro-chemical action for the precipitation of metals in an ornamental form, was Mr. Spencer, of Liverpool.

[166] See Spencer, _Instructions for the Multiplication of works of Art in Metal by Voltaic Electricity. Novelties in Experimental Science_: Griffin, Glasgow, _Elements of Electro-Metallurgy_: by Alfred Smee, Esq.

[167] The magneto-electrical machine is employed in Birmingham for this purpose; but I am informed by Messrs. Elkington that they do not find it economical, or rather that the electro-precipitation is carried on too slowly.

[168] This has been done by Mr. Robert Were Fox, at a mine near Falmouth. By connecting two copper wires with two lodes, and bringing them, at the surface, into a cell containing a solution of sulphate of copper, this gentleman obtained an electrotype copy of an engraved copper-plate.

[169] This has been most effectually accomplished by Mr. Bain. Mr. Hobson has had an electric clock, thus excited, in action for several years.