442

tenders were received on the 10th of May last from the undermentioned companies, viz. :

"The Anglo-American Brush Electric Light Corporation, for the west and central districts.

"The House-to-House Electric Supply Company, for the eastern district.

"The Metropolitan Electric Supply Company, for the western district.

"The Laing, Wharton and Down Construction Syndicate, east district.

"The London Electric Supply Corporation, all three districts.

"These were referred to the engineer and solicitor for consideration, with power to consult Mr. Preece thereupon, and the engineer, in conjunction with Mr. Preece, prepared an abstract of the said tenders.

"In the meantime we received a copy of Major Marindin's report to the Board of Trade on the various applications for provisional orders and licenses under the Electric Lighting Acts, in which he says, in regard to the City, The Commissioners of Sewers, acting for the Corporation, are endeavouring to obtain tenders for the lighting of the City, but I see no reason why the principle that all such lighting should be done under statutory powers and obligations, should be departed from in their case;' and the Commissioners have since received notices from the Anglo-American Brush Electric Light Corporation, Metropolitan Electric Supply Company, London Electric Supply Corporation, and the Laing, Wharton and Down Construction Syndicate, that they will in the next Session apply for provisional orders to supply electricity within the City of London.

"We have also had before us a model form of provisional order prepared under authority of the Board of Trade.

"On carefully considering the tenders sent in, together with the suggestions of the companies, in regard to conditions, it was found that the tender of the Anglo-American Brush Corporation was the only one practically in accordance with the specification, and, under the advice of Mr. Preece, we instructed the officers to negotiate further with the Metropolitan Electric Supply Company and the London Electric Supply Corporation with a view to arrange similar terms with them.

"This has since been done, with the result that they have severally modified the terms of their tenders, so as to bring them into uniformity with that of the Anglo-American Brush Corporation, and, broadly, all these three companies now agree to accept the terms of the provisional orders now sanctioned by the House of Commons.

:

"The prices per annum per arc lamp are as follow:£ s. d. "London Electric Supply Corporation 24 3 10 Metropolitan Electric Supply Company 26 0 0 "Anglo-American Brush Corporation 26 0 0 "But the London Electric Supply Corporation propose to extinguish half the lamps at midnight.

"After full consideration we beg to recommend that the tenders of the said three companies be provisionally accepted, subject to their agreeing to enter into a contract for 21 years, determinable by either party at the end of 7 or 14 years, and the London Electric Supply Corporation waiving the condition as to extinguishing half the lamps at midnight.

"That the three districts into which the City is divided for this purpose be allotted as follows, viz. :— "No. 1, west, to the Metropolitan Electric Supply Company.

"No. 2, central, to the Anglo-American Brush Corporation.

"No. 3, east, to the London Electric Supply Corporation.

"To light the main thoroughfares by means of 395 arc lamps will cost £10,024, in place of 1,730 gas lamps, now costing £5,530 per annum ; but whilst the price will not be double, the amount of light will be many times greater."

In notes appended to this report it is stated that the

[OCTOBER 18, 1889.

London Electric Supply Corporation having agreed to waive the condition as to extinguishing half the lamps at midnight, say the price is to be £26 per lamp; and that all the companies agree to make the contract for public lighting determinable at the end of 7, 14, or 21 years.

Colonel Haywood (the engineer) reports that he has in conjunction with Mr. Preece, prepared an abstract of the various tenders sent in.

Mr. Preece, after quoting from the Board of Trade report, says: "I beg to point out that it appears to me that Major Marindin has not taken sufficiently into his consideration the commercial element that enters so strongly into one side of the question.

"He regards the City merely as a local vestry, with some ancient rights and privileges that have to be respected; but he forgets to note that the amount of lighting, and the capital necessary to be expended in the City, far exceeds that for any other portion of the metropolis. He seems to regard the City as a convenient route or way to enable an electric lighting company to carry their mains from the other side of the Thames to Clerkenwell, forgetting that there is a railway connecting the two places that offers a very convenient route for mains. But the chief point that he has neglected is the £ s. d. point that the guardians of the public interest have to consider so carefully, viz., that the streets may be illuminated with the best artificial light, obtained at the cheapest possible rate. The Commissioners of Sewers have not only to look after the effective lighting of the streets, but they also have to regard themselves as the custodians of the public purse. From this point of view they have to select not only the best and cheapest lamp, but they have to select as contractors to conduct the service, those whose financial position and standing in the City is above reproach. Major Marindin offers very powerful evidence in favour of the lighting of the Metropolis being done rather by rich and large com panies than by small and speculative concerns."

The report of Mr. Preece thus concludes :"The prices that it is proposed to charge for an ordinary arc lamp vary between the limits of £26 and £45 per annum. The proposed distribution of light varies between the ratios of one arc lamp to three ga lamps, and one arc lamp to five gas lamps. In some cases it is quite clear that the desire has been to illu minate the City more brilliantly than any other city in the world, and I think in some cases this has been done to excess. My own view is, that one arc lamp should, on the average, replace four gas lamps, and that the normal arc lamp should not cost the City more than £26 per annum. If this were the case, then the Commissioners would not be called upon to pay much more for electric lighting than they pay now for gas. I think all these points that I have enumerated require further consideration, and I do not feel myself in the position at the present moment to make any definite report to the committee as to the course which it is advisable for them to pursue.'

This is followed by the undermentioned joint report of Col. Haywood and Mr. Preece :

"In accordance with the resolution arrived at at the last meeting of the Streets Committee, we have had several interviews with the representatives of the London Electric Supply Corporation and the Metropolitan Electric Supply Company. The result is that they have each considerably modified the terms of their tenders, so as to bring them to a form uniform with that of the Anglo-American Brush Corporation. Broadly they all agree to accept the terms of the original specification, modified only in terms of the provisional orders now sanctioned by the House of Commons, but not yet passed through the House of Lords.

"The price proposed per annum per arc lamp is as follows:

OCTOBER 18, 1889.]

443

dynamo are utilised in various parts of the exhibition to drive machinery in motion. They are all fitted with a special starting switch mounted on the pole pieces. This consists of a small pivoted lever drawn upwards by a light helical spring, and in work pulled downwards by the pole pieces. The object of this lever is to short-circuit the special series winding on the field magnets. This series winding consists of about 500 turns of comparatively thin wire, and serves the purpose of a temporary resistance in the armature circuit in starting the motor, at the same time strengthening the magnetic field. As soon as the magnets are excited the pivoted lever is attracted on to a small detent which is removed as soon as the armature has attained a speed approaching its full speed. The pivoted lever thus falls to its lowest position, shortcircuiting the series winding by means of a mercury cup. When the motor is stopped the series winding is again automatically introduced into the armature circuit by the rising of the pivoted lever, so that there is no risk of starting the motor without the extra resistance in the armature circuit.

The report concludes with an abstract of tenders prepared by the engineer and Mr. Preece, and certain amendments proposed by the Metropolitan Electric Supply Company and the London Electric Supply Corporation.

BIRMINGHAM EXHIBITION.

WE illustrate here with a small combined plant of engine and dynamo exhibited by Messrs. Laurence, Paris and Scott, Limited, of Norwich.

The engine has a 43-inch cylinder with 4-inch stroke, and runs at about 400 revolutions per minute. It has a steel crank shaft with balanced crank, the bearing surfaces are made very large, and the lubricating arrangements are suitable for continuous running.

The dynamo is one of this firm's D type machines compound wound running at 1,400 revolutions per minute, and it has an output of 14 kilowatts. It is driven by a 4-inch belt, made of thin flexible leather. Owing to the abnormal width of the belt no difficulty is experienced in transmitting the necessary power from the engine to the dynamo although the drive is so very short. The dynamo is provided with sliding rails, so that the belt may be tightened whilst running. Altogether this appears to be a very compact and efficient 20-light plant and runs very smoothly. Steam not being available the plant is shown running at full speed by means of current supplied to the dynamo, which thus works the engine and at the same time puzzles the visitors.

Several motors of the same pattern as this little

One of these motors is shown attached to an ordinary saw-bench, forming a portable saw. Another drives a large Blackman air propeller in the machinery hall where two of this firm's dynamos are at work; one driven by Messrs. Crossley's 9 H.P. gas engine has a normal output of 90 ampères at 100 volts, and the other, driven by Messrs. Robey's new high-speed compound engine, has a normal output of 120 ampères at 100 volts. This machine has, however, on one or two occasions been run at considerably over its normal output. All these machines have deep and narrow slots cut in the drum armatures to receive the winding, which is thus securely embedded within the body of the laminated iron drum. The field magnets are made of a special cast iron, and this, together with the peculiar construction of the armature, makes the size of these machines seem small for their output and speed. The speed of the 120-ampère machine, when giving 100 volts, is 725 revolutions per minute at full load and 760 revolutions per minute with no load, so that it is "over-compounded" about 5 per

cent.

We understand that Messrs. Laurence, Paris & Scott, are busy with several important improvements, notably a new meter for the use of electric supply companies, which is expected to take a very high position amongst its competitors.

444

INDUCTION AND OTHER THINGS.

(Continued from page 412.)

LAST week, when discussing the practical unit of selfinduction, we hinted that coefficient of self-induction was not length. Some writers make out that coefficient of self-induction is length; others say it is of the nature of length, which seems to be merely a roundabout way of saying it is length; others write of a coefficient of self-induction of so many centimetres; and more say that the coefficient of self-induction is measured by a length. This is a vague sort of statement, but seems to be a guarded way of saying that it is length. Many writers bring forward an example or two to show that what they say has a physical meaning. Thus Dr. Fleming, wishing to show that current is the square root of force, whatever kind of entity that may be, instances somewhere in his book the case of a dynamometer, where the force varies as the square of the current. We see no logical connection between the nature of electric current and the force on dynamometer coils. The example might be used equally well to show that as the force varies as the turns of copper wire in one of the coils current is the same as turns of copper wire, that is to say, it is elongated copper wrapped with silk. This is nonsense, due to the omis sion of "number of " before "turns of copper wire."

Similarly, the usual example of the physical meaning of resistance as velocity can be used to show that electromotive force or current or anything else is velocity.

If the fact that the number representing the speed of a bar of unit length running along a slide across unit field developing unit current in the circuit is equal to the number representing the resistance of the circuit, it shows that resistance is of the nature of velocity; the fact that the number representing the electromotive force is also equal to the number representing the speed goes to show that electromotive force is also speed.

We

When the youthful mathematician multiplies apples by pennies he is jumped upon; but if his teachers do the same thing there is supposed to be some deep and hidden meaning in their practice. We approach this mysterious subject with trepidation, for, as a glance at the 14th Report of the Association for the Improvement of Geometrical Teaching, of all books in the world, will show, some people think apples may be multiplied by pennies with perfect rectitude. prefer, however, to adhere to the traditions of our youth. When we wish to know the price of a dozen apples at two pence each we do not operate upon the apples or the coins themselves; we take the number of apples and multiply it by the number of pence each costs, and divide the number obtained by the number of pence in a shilling. We even go so far as to say length squared is not area, and that all mathematical operations are performed on abstract numbers only. We depart from one tradition of our youth, however, and hold that it is incorrect to say, "Twice two are four." Two is (not are) the name of an abstract number, and is therefore singular in number. Twice is a numeral adjective, and does not alter the number of the qualified noun. We therefore say, "Twice two is four."

In many text-books in which the "Dimensions of Units" are discussed, it is stated at the beginning that, for instance, [L] is the concrete unit of length; after a little it is found that [L] is really what Prof. James Thomson called the change ratio of the unit of length; that is, it is simply a ratio of the new unit to the old, the number of times one will go into the other. Sometimes it appears to come on the scene as the ratio of the new unit to the old one, and later on it becomes length itself; in fact, a fallacy is apt to creep in. Even if we were to assume that a symbol could represent a concrete unit, we must suppose that when one concrete unit is divided by another concrete unit with a different numeric, the concreteness cancels out, and leaves simply bstract number. If M, L, and T are numbers, or ratios, of course such ideas as resistance being at once becomes nonsense. Writers also often

E

[OCTOBER 18, 1889.

use suche xpressions as C = In the first place, a!!

R®

that can be said is that the number represented by C is equal to the number represented by E, divided by the number represented by R; and this is only true in a consistent system. Generally speaking, the sign = should be replaced by the sign of variation, x. Dr. Fleming, in one place, says that in a particular equa tion = means "is measured by," = can mean nothing but" is equal to." 2 x 2 = 4 means that two malt. plied by two is four; not that it is measured by four At other times Dr. Fleming uses the expression "s numerically equal to," whereas no other sort of equality exists in mathematics.

It is a curious fact that a slip is made in Maxwell' dimension table where the "dimensions" of K in the electrostatic system and μ in the electro-magnetic are given as zero. Of course they should have been either 1, or [M° Lo To]. It is still more curious that this slip is copied into every, or almost every English text-book. It is corrected in Joubert and Mascart's treatise. Similarly, to be perfectly consistent, such dimensions as, say, of capacity in electrostatic measure should not be given as [L], but as [L' Mo To]; M and T need not be suppressed for the moment. It is strange that a writer who would talk of a coefficient of self-induction of a kilometre would never talk of the cosine of the mag. netic inductive capacity of; he would feel that there was some suspicion of nonsense there, though the dimensions are all right. Magnetic inductive capacity must be of the nature of an angle, or must be an angle, or must be measured by an angle, we do not care which.

So many great men multiply apples by pennies, that we must modestly remind readers that, as an eminent judge said, it is unnecessary to insert here and there "in my humble opinion," or "I think," as nobody writes anything more than his mere opinion.

Let us take it, however, that concrete numbers can be multiplied together, or that pairs of a concrete and an abstract number can be multiplied to give a concrete result, and see where we get to.

We are now so accustomed to the use of dimensions that it is quite natural to talk of the Scotch express going at so many microhms, or of the South Eastern trains as travelling at so many megamhos; so it would be difficult to get people to see the least absurdity in such expressions. Let us therefore go to some other branch of science.

Jevons, in his "Theory of Political Economy," uses dimensional formulæ. His concrete units are [M], [T] and [U]. [M] and [T] are mass and time, but [r] is the concrete unit of utility, a quantity which has, we fear, little to do with the subject under discussion. Without going into economic questions we may call [U] the concrete unit of exchange value, and we may define it in terms of [L] so as to get a correspondence between physical and economical systems. A C.G.S. unit of exchange value should, of course, be ridi culously small or outrageously large. As the concrete unit of mass is a cubic centimetre of water we will take as the C.G.S. [U], the value of a cubic centimetre of cold water. Economists point out that water has no value till labour has been spent on it, or unless it is scarce; our unit will therefore be a cubic centimetre of water delivered on the premises. This may be called the "stiver." The term may be spelled backwards to give the absolute unit of poverty. We have interviewed the water companies, and find the stiveroon is somewhere about threepence. The dimensions of income are thus [L3 T'], while the dimensions of area are, of course, [L]; it is therefore perfectly correct to talk of a resistance of a hundred pounds a year per acre. We sometimes wonder what posterity will think of us. If the New Zealander of Macaulay, or our prototype, or of whoever invented him, sitting on the ruins of St. Paul's, picks up a thing like a milestone labelled on one side "To Hanwell, one thousand pogglets," and on the other "From Colney Hatch twenty-five guinea megfarads per microhm per cubic second," what will he think of the common sense of the Nineteenth Century?

OCTOBER 18, 1889.]

When we urged that only abstract numbers could be multiplied together or divided one by another, it was not forgotten that people might say that that is not the case, because vectors can be multiplied, and they are not mere numbers, but represent both length and direction. A vector does not represent direction, but relation of one direction to some other, or standard direction. This ratio of directions is purely a convention, and is represented by an abstract number. Similarly, the product of two vectors is the number of times a unit area will go into a conventionally produced area, and to give this a new direction another abstract number has to be taken into account. The other part of the product is the number of times a unit volume will go into an imaginary volume conventionally produced.

The application of vector methods to a subject like electricity where, for instance, motion, induction, and electromotive force act at right angles to one another seems almost to give the methods a physical meaning. It also seems to render the treatment of such subjects very much simpler. Such an expression as

is, to say the least, somewhat tedious reading. Mark Twain would say it had a perspective. It was somewhat foreshortened in the original by the use of brackets. It can also be written out more fully, so as to appear even more impressive.

It is exceedingly difficult to follow the meaning of such expressions as this, especially if one is reading, say, on the top of an omnibus. Even if one can draw, a representation of all this on a plane in Chinese perspective is confusing. To imagine such expressions is akin to playing chess blindfold. How much simpler this is when put into the form,

which means it all. Whichever method is best alone, we think students with limited time have reason to complain when both are used and mixed up together. Dr. Fleming deserves the thanks of the community for using block letters instead of German capitals. It is very annoying in one's reading to come across a thing like a tangle of snakes, and either have to wait till a German dictionary is accessible or guess at what is supposed to be represented.

While on this subject it may be mentioned that Dr. Fleming seems to have made a slip in his definition of Maxwell's "curl," and to have confused it with the. line integral of the component of a vector round a finite closed curve. Thus, to find the curl of the magnetic force at a point, an element of area is described there and turned so that the line integral of the magnetic force round it is a maximum. This line integral is the curl of the magnetic force, and is taken as a vector normal to the little area. The curl of the magnetic force at a point is thus four times the current density. (To be concluded.)

Electric Lighting at Portsmouth.-The publication of the prospectus of the Portsmouth and South Hants Electric Supply Company, Limited, has occasioned quite a sensation, the list of directors and founders showing that the new undertaking is being backed up by many of the leading men in the town. The Commander-in-Chief, Admiral Sir Edmund Commerell, V.C., G.C.B., and several of the principal physicians at Southsea are among those who have a substantial stake in the company, which has decided to lose no time in obtaining the necessary Parliamentary powers. The Laing, Wharton and Down Construction Syndicate have also lodged an application with the Board of Trade for a provisional order enabling them to instal the electric light in Ports mouth.

LIGHTNING CONDUCTORS.

By S. ALFRED VARLEY.
(Continued from page 380.)

ENERGY.

445

WHAT energy is, and how it becomes associated with, and is stored up in matter, is involved in the deepest of mystery. We see it unlocked in the fire grate in the shape of heat and conveyed to the cylinders of the steam engine, where it diappears, and mechanical force takes its place. A little further on, the mechanical force produced in turn disappears, and the energy in some mysterious manner becomes transferred to the electricity of the dynamo system. The insulated wire of the dynamo circuit and the magnetic field in which the armature revolves form parts of a complete system, and to any spot within the limits of this system, the energy, now it is associated with electricity, can be silently conveyed to produce light, heat, mechanical force or chemical action.

Although we know nothing in respect to the nature of energy itself, we know it to be indestructible, and that, unlike electricity, which cannot be added to, or taken from matter, energy is capable of being added to and taken from it; the quantity of energy which can be imparted to matter or associated with the electricity of matter, seems also to be unlimited. The movement of matter in the performance of work, or the movement of electricity in matter, involves the overcoming of resistance.

Energy itself is indestructible, and the only thing that can happen to it is, that it may become changed into a shape useless to ourselves, and whenever it is associated either with matter, or with electricity, a certain percentage of it does become changed and is so lost. Now, for energy to be available for useful purposes, it must be associated either with matter, or electricity, but the greater the quantity of matter, or of electricity, a given amount of energy is associated with, the greater the percentage of energy which becomes lost from its being changed into a useless form, and therefore the transmission of energy through the medium of electricity will be found to follow what the writer in an earlier part of this article ventured to suggest as a general law governing the transmission of energy, viz., that the greater the amount of energy relatively to the vehicle of its transmission, the more perfect and complete will be the transmission.

In the examples previously given it was assumed that the resistance encountered in the electric circuit was that opposed by the metallic conductor, and that the internal resistance of the voltaic couples which set up the electrical motion was small enough to be a negligible quantity. Let a case be considered where opposite conditions prevail, and where the resistance of the metallic conductor is so small as to be practically inappreciable, the quantity of electricity set moving under such conditions will be determined by the internal resistance of the voltaic couples, and adding to their number will not appreciably increase the quantity of electricity, as each additional couple brings with it its own internal resistance, and consequently the resistance and the electromotive force become increased in the same ratio. The energy will, however, be increased in the same degree as the electromotive force becomes augmented, and there is theoretically no limit to the amount of energy which in this way may be associated with electricity, any more than there is theoretically a limit to the velocity, and, consequently, to the energy which can be imparted to matter.

The form which energy takes when combined with electricity, by adding to the number of voltaic couples, is that of potential or pressure, and its relationship to the electricity it becomes associated with, is very analogous to that of energy combined with matter in the form of high-pressure steam, water in a high-pressure hydraulic system, or a rifle bullet to which a high rate of velocity has been imparted.

446

We see, therefore, how perfectly matter and electricity in motion harmonise with one another, at least so far as the transmission of energy is concerned; there is, however, a difference between electrical motion and matter in motion which should not be overlooked; this difference arises out of the fact that when electrical motion is occurring the electricity set in motion is part of the conductor itself, and nothing is added to, or taken from the electrical system, whereas when energy is being transmitted through the medium of, say, a steam engine, or a hydraulic system, matter associated with energy enters the cylinders and pipes at one end and passes out of them, after parting with energy. Let us briefly consider what occurs in a hydraulic system through which water under pressure is being forced, and which is performing work, and let it be assumed a portion of the system is composed of pipes whose diameter is larger than that of the other parts, the pipes throughout their entire length will be subjected to an internal pressure tending to burst them, and the stress to which the system becomes subjected, will be greater where the pipes are larger, directly, as the internal diameter of this portion of the system is greater than that of the other parts. Now, in an electrical system, a portion of which is formed of a conductor whose section is larger than that of the other parts, the very reverse of what has been just described occurs, the electrical pressure tending to burst up the conductor is less where the conductor is larger, inversely as the sectional area of it is greater.

I proceed to analyse very briefly the action that takes place when matter is broken down and built up in a decomposition cell or plating bath.

Fig. 8 represents a voltaic couple, whose circuit is completed through two copper plates immersed in a solution of sulphate of copper.

When the circuit is completed, a current passes from the pole of the voltaic couple to the left hand copper plate, through the sulphate of copper solution to the right hand plate, and back through the conductor to the pole.

The electric current set up by the breaking down of the zinc and water molecules in the voltaic cell develops a corresponding action in the plating bath, the left hand copper plate becomes broken down, molecule by molecule, and new molecules of metallic copper are built up on the right hand plate. The rate at which the breaking down and building up of metallic copper occurs has reference to the rate at which the zinc in the voltaic cell is oxidised, and this rate is determined by the total resistance of the circuit. The actual weight of copper broken down and built up in the plating bath, compared with the weight of zinc oxidised in voltaic cell, is relative to the difference of their respective atomic weights. The atomic weight of zinc 32.52, and that of copper 31-66, and therefore 31-66 parts of copper will be broken down and built up in the plating bath for every 32:52 parts of zinc broken down in the voltaic cell.

=

[OCTOBER 18, 1889.

broken down and built up in the plating bath also at a similar rate.

Energy is concerned in the building of atoms into molecules, much in the same way as it is concerned in the structure of buildings where bricks and stonework have to be raised and fitted into their respective places, and when molecules are resolved again into atoms, energy equivalent to that originally concerned in building them into molecules becomes unlocked and set free. Now, in the plating bath the energy unlocked by the act of breaking down the molecular structure of the left hand positively charged plate becomes transferred to the right hand negatively charged copper plate, and becomes there locked up in the new molecular structure created, the only work performed being overcoming the resistance which all circuits in a greater or less degree oppose to electric motion.

Fig. 9 represents a voltaic couple connected throngh three plating baths opposing three times the resistanc of the single bath, the rate at which zinc will be broken down in the voltaic couple will be decreased to frd of an ounce per hour, and copper will be broken down and built up in each cell at the rate of rd of an ounc per hour; but as there are three batus, an ounce of copper per hour will be deposited at one-third of the cost for zinc.

The question may be fairly asked if the economy with which plating operations can be effected becomes greater when more than one bath is employed, why not increase their number indefinitely. The answer is to be obtained by sitting at the feet of Nature. If we only do this we can hardly fail to observe Nature does not love extremes; her laws, it is true, are absolute, and never vary; she governs, however, not by one but by many laws, and the phenomena presented to our gaze are due, not to a single force of law, but to a com position of laws or forces. The practical impossibility of obtaining a really perfect vacuum is a case in point the compression of gases is another example. Gases resist compression within certain defined limits, when another law asserts itself, which causes the molecules to come closer together, then mere compression is capable of effecting, and converts the gaseous molecules into an incompressible liquid; other illustrations could also be given from mechanical science.

In an earlier portion of this article it was pointed out that a statical charge was storage of energy. In connection with the so-called "impulsive rush experi ment," the well-known fact was incidentally referred to, that when a Leyden jar or a charged cloud dis charges into a condenser, the potential of the electricity becomes reduced directly as the capacity of the con denser into which the discharge passes. It was further pointed out that two platina plates immersed in water or acid and water, formed a Leyden arrangement of lo resistance and large capacity relatively to ordinary glass Leyden jars, and that a Leyden arrangement so con structed might be regarded as a connecting link betwee the storage battery and an ordinary Leyden arrangement The writer now hopes to be able to demonstrate there is no hard and fast line which separates a Leyden ja from the most perfect conductor conceivable; that, it fact, paradoxical as it may appear, a perfect conductor becomes an insulator, and for the simple reason that i a theoretically-perfect conductor the conducting capa bilities have been carried to such extreme limits, that another law comes into play somewhat similarly to wha is recognised as occurring when gaseous matter is subjected to extreme pressure.

An electroplating bath differs so far from a cell con structed with two platina plates separated from on another by water, or other electrolytic liquid, that cannot be properly regarded as a Leyden arrangement The water of the platina plate cell when a current passing becomes decomposed, oxygen being deposite in a condensed and very active form on the plate cot nected with the pole of the circuit, and hydroge being deposited in a condensed form on the platin plate joined to the pole, the oxygenized pla becomes statically charged with electricity and th hydrogenized plate receives a + charge. The quantiy