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to Frankfort. By the use of a subsidiary steam or other engine to put the second alternate dynamo in step, the necessity of a third wire will, we suppose, be obviated.

The Supply of Power from Central Stations.About 20 years ago a bequest of £500 was made to the Society of Arts by Mr. T. Howard for the purpose of presenting a prize to the author of a treatise on motive power. The prize having on several occasions been offered without any practical result of value, the council considered that the most useful way of dealing with it would be to invite some eminent authority to deliver a course of lectures on a subject coming within the terms of the trust, on the understanding that the lectures should afterwards be published as a treatise. The result was that Mr. Anderson delivered, in 1884-5, the valuable course which were afterwards republished under the title of "The Conversion of Heat into Useful Work." Since that time the interest of the fund

has accumulated to a sufficient extent to allow the council

to repeat their action, and they have accordingly invited Prof. Unwin to deliver, during the next session, a course of lectures on "The Generation of Power at Central Stations,

and its Distribution therefrom."

London County Council.-Sanction is given by the London County Council to mainlaying by the Kensington and Knightsbridge Company at Rutland-gate; to the Electricity Supply Corporation across the Strand to the Adelphi, to Northumberland-street, Whitehall, Charing Cross, Trafalgar-square, Pall-mall, St. Martin's-lane, Haymarket, and Leicester-square; to the Westminster Company in Buckingham-street, Queen Anne's-gate, Downingstreet, Richmond-terrace, Parliament-street, Great Georgestreet, Broad Sanctuary, Victoria-street, etc.; to the London Electric Supply Corporation for trunk mains London Electric Supply Corporation for trunk mains from Cockspur-street through St. St. James's Park Buckingham-gate; to the Metropolitan Company, in Leicester-place and across Cranbourne-street. The Parliamentary Committee report that in the opinion of the Highway Committee, in which they concur, the substitution of the Vestry of Chelsea for the Council as electric lighting authority in that parish would be unsatisfactory, and that they have directed a petition to be prepared and, if necessary, presented against the Bill.

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Conversazione.-The president of the Institution of Electrical Engineers (Mr. William Crookes, F.R.S.) and Mrs. Crookes received a brilliant company of over 800 guests at a conversazione in the galleries of the Royal Institute of Painters in Water Colours, on Monday. The visitors greatly enjoyed the very fine exhibition of portraits, the band of the Coldstream Guards, the strawberries, and coffee-ices, and interchange of social amenities. Besides the members of the Institute-Sir Wm. Thomson, Mr. W. H. Preece, F.R.S., Mr. J. W. Swan, Dr. S. P. Thompson, Prof. Ayrton, F.R.S., Prof. Perry, F.R.S., Dr. Hopkinson, and others were many noted guests, among them being Sir F. Abel, K.C.B., Sir James Douglas, Dr. Gladstone, F.R.S., Earl Russell, Duke of Marlborough, Sir Edwin Arnold, Sir F. Bramwell, F.R.S., H. Perigal, F.R.A.S., General J. T. Walker, F.R.S., Sir Benj. Baker, K.C.M.G., Sir G. B. Bruce, Hon. H. A. Dillon, Sir Philip Magnus, Sir E. J. Reed, Sir H. Doulton, Mr. W. J. Karner and Mr. E. L. Corthell (Chicago Exhibition), Mr. Wimshurst, Mr. Ferranti, Dr. Ernest Hart, Mr. Ganz, and many others.

Electrical Manufacture of White Lead.-In an article in the Revue Industrielle for July 4, the electrolytic process of forming pure white lead is discussed from its theoretical and practical points of view. The description is given of a commercial process recently patented, the adapta

tion of a well-known laboratory experiment. In a suitable vessel is prepared a solution of nitrate of ammonia and nitrate of soda, five parts by weight of each to 100 parts of water. Two pigs or plates of lead are placed therein, and the bath is saturated with carbonic acid in a nascent state. This is economically obtained by burning lime. When the bath is rendered almost neutral, the two pieces of lead are put into connection with the poles of a dynamo giving 15 amperes per 100 square centimetres of surface of lead in contact with the positive electrode. As soon as current passes, white lead appears at the surfaces of the two pieces of lead, and by continuing to saturate the bath with the whole can be transformed into white lead, which is carbonic acid, and prolonging the passage of the current, then taken out of the bath, washed in a 6 per cent. solution of salt water, and dried, producing a commercial solution of salt water, and dried, producing a commercial product with exceptional covering qualities, composed of one part of hydrated oxide of lead to two of carbonate of lead. The only expense of manufacture after the bath is set up is in the production of the carbonic acid and the current, and this is stated to be considerably less than that of the present forms of apparatus in outlay, wages,

and time.

the study of fact, by the evolution of theory, the adaptation Registering Instruments.-Science progresses by of theory and fact to use, and the consequent study of results. In science, to have results is not enough: we must have records of these results, records from day to day, from year to year. Therefore, the success which attends all really good attempts to satisfy the demand for registering instruments. No firm has done more in this of Richard Frères, way than the well-known one 8, Impasse Ferrard, Paris, whose London branch is 43, London-wall (manager, Mr. J. A. Berly). We have before us their catalogue of measuring, controlling, and self-registering instruments for scientific and industrial purposes. "We manufacture," they say, "every kind of registering instrument that may be required in science this catalogue the instruments they desire, we will, on their and industry. Should any of our customers fail to find in indication of the results they have in view, and the phenomena they intend to control, study the type of registering instrument suitable for their purposes," and endeavour to bring out such an instrument. They produce three kinds of measuring apparatus-engineering, electrical, philosophical. Their list of medals and awards is very numerous, embracing those from 1845 to 1890. We find in the catalogue registering anemometers, barometers, chronographs, dynamometers, hygrometers, speed recorders, water-level indicators, pressure gauges, pyrometers, thermometers, volt and ammeters, charge and discharge recorders, and recording electricity meters, besides nume rous others in special departments of meteorology. We advise all electrical engineers to possess themselves of this valuable catalogue.

Chelsea. The Select Committee of the House of Lords

last week, presided over by Lord Basing, considered the Electric Lighting Bill to confirm a provisional order granted by the Board of Trade to the New Cadogan and Belgrave Electric Supply Company, Limited, to enable the company to supply the electric light to a part of the parish of St. Luke, Chelsea. The Bill was opposed by the Vestry of Chelsea on the ground that it made the London County Council the local authority under the order. Mr. T. Holland, clerk to the Vestry, said the Electric Lighting Act of 1882 and 1888 specified the Vestry as the local authority for all purposes under the Acts, and Parliament never intended to give control or powers over electric lighting to any other body than the local authority as

defined by these Acts. By making the London County Council the local authority a concurrent jurisdiction would be established, which might, and probably would, lead to a conflict between the Vestry and the County Council, and when the Vestry became the undertakers the County Council would exercise an authority over their supply, which should be left to the inhabitants of the district. The chairman said he saw no reason why the

Vestry should not be the local authority. Mr. Cripps, parliamentary agent, representing the London County Council, said the Vestry raised no objection to the Council being the local authority under the order of the London Electric Supply Corporation of 1889. Mr. Holland replied that that order extended to nearly the whole of the metropolis, and the parish of Chelsea only formed an integral portion of that area. Therefore, the undertaking could not in any sense be regarded as a local one. The chairman said the committee were unanimously of opinion that the Vestry ought to be the local authority under the order. The Bill was amended accordingly, and ordered to be reported to their Lordships' House. These propositions were made to the House of Commons Committee by Mr. Moon, chairman of the Electric Lighting Committee, and Mr. Whitmore, M.P., but rejected. As seen above, Mr. Holland succeeded in carrying them through the House of

Lords Committee.

Gas v. Electricity at Leeds.-Mr. Walter Rowley, M.I.E.E., Meanwood, Leeds, writing to the Leeds Mercury, has some very apropos remarks upon Mr. Preece's paper last week before the Incorporated Association of Municipal and County Engineers. "Such a statement of facts from the chief electrician to the General Post Office," says Mr. Rowley, "is one that cannot fail to direct the attention of all municipal bodies to the subject, and not allowing such considerations as existing gas works to retard or diminish the adoption of a form of lighting which, on account of its cleanly and sanitary nature, is far preferable to gas. The figures given by Mr. Preece are a remarkable confirmation of the statements made by Alderman Spark when the discussion in the Leeds County Council took place, and we are indebted to him for the very manly way in which he fought for the electric light. Although defeated in their efforts to secure for the town an efficient and cheap electric lighting system, the minority which Alderman Spark represented will before long be shown to have taken the right position. The effect of handing over the lighting of the town to private companies will be that they will only take their systems into the thickly-populated districts, unless compelled to do otherwise; ratepayers in districts farther from the centre of the town, having equal rights to the supply, being left unprovided for. The lighting of a town is one of the duties which ought to be fulfilled with the greatest economy by the local authorities rather than by private ventures. After such a statement as that of Mr. Preece, it must be admitted that electric lighting has now fairly passed out of the experimental into the really practical stage; and, on behalf of those who know the advantages of electric lighting for domestic purposes, this appeal to the authorities is made, and I would ask all to rise above party feeling in this matter, and combine in an effort to secure with as little delay as possible the supply of the electric light to all ratepayers who desire it. The question is one that claims the serious and unbiassed consideration of those upon whom rests the responsibility of supplying (or refusing) a want which all who are intimately acquainted with the subject believe to be a requirement in the public interest. The importance of this matter has induced me to address this letter, in the

hope that, even at the eleventh hour, the attention directed to the subject may have the result of making the supply, under existing circumstances, as extensive and complete as possible."

Trial of the Gordon Electric Car,-At Messrs.

Merryweather's works, Greenwich, on Tuesday, we had the pleasure of witnessing a trial run of the Gordon closed

conduit electric railway. As it is not improbable that a long section of tramway may be shortly fitted up with this system, it may be worth while drawing the attention of tramway and electrical engineers somewhat forcibly to this system, a paper about which was read by Mr. Gordon himself at the Tramways Institute meeting last week, reproduced elsewhere. A line of tram rails exists at the back

The con

of Messrs. Merryweather's works, and this line has been fitted up by Mr. Gordon as an experimental line. car trolley completely fitted with motor gears and switching apparatus is in actual working order, and seems to behave admirably. The principle adopted by Mr. Gordon is ingenious, and the working out of it not less so. duit carrying the current for the motor is a very small one, some 2in. or 3in. of ground being quite sufficient to contain it. The supply rail is laid midway between the two line rails, and consists simply of flat iron laid in concrete in lengths of about 8ft., or one-third the length of the car. The system arranges for charging these sections by the full current of, say, 400 volts, as the car progresses, so that no section is charged 'except those under the car. This is done by a system of connections laid in a gas-pipe with tee-pieces connecting to each length and leading back

a commutating box, which is the feature of the system. These boxes are placed every 100 yards under the kerb, and contain strong long-pull magnets, one for each section. As the car progresses, a shunt current comes back from the section No. 1 to the magnet No. 2, which rises and puts section No. 2 into connection, cutting off No. 1, and so on, as the car moves-the main, of course, running the entire length of the road. These boxes are of very strong construction, and, as seen on the trial, act with precision and force, being able to withstand rough usage. The current being turned on, the car moved forward at considerable speed, and it is interesting to watch magnet after magnet rise and fall, like the keys of a piano, one after the other with absolute precision and not the least sparking. The pull of the magnet is about 7lb., and evidently is more than ample to do its work. The car was run backwards and forwards by Mr. Gordon, under complete control, nothing more being required than the movement of the car switch, which acts both as resistance and as reverser. The advantages of the system are the

use of the closed conduit-no slot or wires that can be touched being needed; the small cost of conduit, and corresponding small cost of alteration of track. Not the least effective advantage of the Gordon system is that, by the addition of one contact, the absolute metallic return for the current can be made by way of the section behind, and thus the difficulty with the telephone companies can be avoided-a matter impossible of arrangement with most systems without costly additions to the mains. The cost of alteration of track and laying the electric conduit is estimated (the figures being checked by Messrs. Merryweather's engineer) as £2,000 per mile, of which £25 each is the cost of commutator boxes. The cost of a new electric car would be £400. Mr. Gordon, allowing all possible contingencies, estimates the actual cost of traction 24d. per car mile. As to the commutator boxes, our opinion is that these will do their work, and are not in the least more fragile than the commutator bars themselves of the dynamo.

TELEPHONE TRANSMITTER PATENTS.

BY A. R. BENNETT.

No doubt the directors of the National Telephone Company believe that there are good grounds for the warning recently conveyed to the public by their advertisement re the Hunnings, Blake, and Crossley transmitters that those patents are really valid, and that they are performing an act of kindness in cautioning all and sundry against them.

But it does not follow that their advertisement should be

accepted without discussion. It would be sorely against the public interest to suffer telephone enterprise to be crippled, and development arrested for another 18 months, simply out of deference to the not altogether disinterested opinions of the National Company's directors. Their duty to the shareholders would require them to put the best complexion on the matter, even though they had their doubts, and it behoves those interested from the opposite point of view to examine their statements and judge for themselves whether they can be substantiated or not.

I have recently had occasion to enquire somewhat narrowly into the actual status of the very three patents mentioned in the advertisement, and I have much pleasure in acceding to the suggestion that I should make public

my

conclusions and the reasons for them.

In the first place, I consider that the National Company is apparently inclined to attach far too little importance to the labours of our distinguished countryman, Prof. Hughes. A good many months before the date of the first secondary patent Prof. Hughes showed how more efficient telephonic transmitters than any devised by Edison could be con structed out of conducting powders and fragments of

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F. Fig. 24 is a diagram of a microphone and battery in secondary is to line and earth. the primary circuit of an induction coil, of which the

It may be remarked, however, that Edison had no right to claim this combination, since Dr. Wright as far back as 1867 used an induction coil in connection with a Reiss transmitter, and Cromwell Varley afterwards employed it with his musical telephone.

Edison's Fig. 10, which is reproduced, shows a microphone carrying two platinum discs, against which are pressed plumbago points mounted on springs, the pressure between the platinum and the plumbago being regulated by adjusting screws applied at the base of the springs. The expiry of Edison's patent of July 30 therefore frees :

1. Diaphragms fixed at their edges.

2. Variable resistances resulting from greater or less intimacy of surface contact. This is practically the microphone. 3. Lampblack (soft carbon).

4. Springs for carrying microphonic contacts.

5. Screws for regulating the pressure exerted by the

springs.

6. Combination of microphone, battery, and induction

coil.

So after July 30 any person will be free to use any or all of these factors, provided he combines them in a manner not effectually protected by subsequent inventors.

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charcoal; but inasmuch as Edison was before him with his tension regulator patent (No. 2,909, of 1877), and that patent mentioned variable contacts and carbon in the form of lampblack, it was held that Hughes's discoveries were anticipated and covered by Edison. As a result, the expiry of Edison's patent on July 30th next will not only set free all the forms of transmitters described in it, but also all the forms invented by Prof. Hughes, and will further allow of some of Edison's transmitters being improved into really efficient instruments by the substitution of hard carbon for the plumbago points and semi-conducting tufts originally imagined.

Edison's specification is a voluminous one, and amongst a mountain of dross contains, comparatively, but few grains of gold. Before proceeding to the examination of the three chief secondary patents, it would be well, therefore, to briefly indicate the chief points he makes, and ascertain what features of value become free in August through the lapse of the Edison rights.

The passages in his specification bearing most on the practical question are as follow:

EDISON (NO. 2,909, JULY 30TH, 1877).

A. Page 5, lines 6 to 16.-Description of diaphragm preferably but not necessarily of mica, secured at its edges. Amongst others Edison mentions diaphragms of metal.

B. Page 6, line 5.-"In some cases I make use of a variable resistance resulting from greater or less intimacy of surface contact.

C. Page 6, line 31.-"In some instances I make use of the best quality of lampblack."

D. Page 7, line 15, Fig. 10.-"h is a resonant chamber at the end of which is the diaphragm 10, and at each side of this diaphragm there are springs, C2, C3, having points made up of compressed plumbago. These points

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EDISON'S FIG. 10.-10, diaphragm; h, mouthpiece; c2, c3, springs ; c4, c, contacts; s1, s2, regulating screws.

The discoveries of Hughes already alluded to increase the foregoing free list by the addition of hard carbon, multiple surfaces, and conducting matter in the form of powder. It will be permissible to combine or interchange Edison and Hughes's discoveries. With such material at command, the telephone engineer who cannot design an efficient transmitter and still keep clear of Hunnings and Blake, may reasonably be adjudged to have mistaken his vocation.

I shall now submit the secondary patents to some analysis with the view of ascertaining how far they are original, and whether they do not run some risk of being indicted as (to borrow a term from the National Company's advertisement) "colourable imitations."

HUNNINGS (No. 3,647, SEPT. 16TH, 1878). Hunnings's claim is essentially for the use of fine powdered carbon confined in a loose state between two metallic diaphragms, one of which is vibrated by the voice.

Hunnings preferred thin platinum foil for his vibrating diaphragm, and seemed to consider a metallic or a metalcovered diaphragm indispensable. That is what he foreshadows in his provisional and claims in his final, and there is no suggestion as to the practicability of using diaphragms into the composition of which metal does not enter, except in one place in the final, where, after enumerating platinum, iron, and silver, he adds "or other material." But it is evident that if "material" is not actually a misprint for metal, the other material he had in view must have been metallic in its nature, since no allusion is made to the special contact or electrode that would be necessary were wood or other non-conducting material employed.

Hunnings's own words may be quoted as showing what he believed to be new in his invention. After disclaiming

any right to Hughes's microphone and Edison's carbon telephone, he says: "But what I believe to be new and desire to claim as my invention under the herein before-in-part recited letters patent is 1. The use of finely-powdered carbon, or like conductor (preferably oven-made engine coke prepared as described) in a loose and free state (not compressed or consolidated in any way or combined with foreign material) as a means of varying the resistance of a telephonic circuit by the vibrations of a thin metallic or metalcovered diaphragm enclosing it, controlled by the sound-waves

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The point is of importance, because about nine months later Marr (No. 2,497, June 21, 1879) protected a transmitter of powdered carbon confined between two wooden diaphragms, having carbon discs attached to their centres as contacts. This combination, although invented by Marr, was generally known as the Moseley transmitter. The patent is now void, and if held free of Hunnings, would be open to all after July 30.

Subsequently, Moseley (No. 1,320, January 30, 1885) and Berthon (No. 2,893, March 4, 1885) employed powdered carbon confined between diaphragms of thin carbon plate. Of these, Moseley's has lapsed, but Berthon's is still in force, although its validity in face of Moseley's prior claim for granulated carbon between carbon diaphragms is considerably more than doubtful.

The diaphragm is not the only weak point about Hunnings's, for Hughes, in his paper before the Physical Society (Nature, June 27, 1878), stated that he had discovered that a current passing through conducting matter in a divided state, either in the form of powder, filings, or surfaces, was varied under the influence of the slight pressure applied by sonorous vibrations. This specific mention of conducting powder by Hughes four months before Hunnings applied for his patent, precludes the latter from claiming any exclusive right to powdered carbon.

Again, on June 3rd, 1878, three and a half months prior to the date of Hunnings's patent, Prof. Blyth, of Glasgow, described in a paper to the Royal Society of Edinburgh (Nature, June 13, 1878), a transmitter consisting of pretty coarse fragments of gas cinders packed in a shallow box of thin wood, having tin (tinned iron ?) strips at the ends to serve as contacts. The results obtained he described as satisfactory, although there was no front vibrating diaphragm. I have recently had an experimental transmitter made to Blyth's description, and find it is really an efficient instrument. The box speaks equally well, and very well, whether the voice is directed against the sides, bottom, top, or ends. By substituting carbon electrodes for Blyth's

Front.

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FIG. 2.-Details of an Efficient Transmitter outside the Secondary Patents that may legally be used after July 30th. BC, brass clamp; CC, carbon contact; CB, carbon block; D, diaphragm; IR, indiarubber ring; M, mouthpiece; RS, regulating screw; S, spring; T, terminal screw.

impinging upon it. 2. A telephone transmitter consisting of a layer of finely-divided carbon or similar conducting material, preferably oven-made engine coke, placed in a loose and free state between the thin metallic or metal covered diaphragms in a suitable case, and for the purposes described." Since these claims avowedly cover all that Hunnings believed to be new, and expressly exclude all but metallic or metal-covered diaphragms, it surely would not be complimentary to Hunnings to rule that he meant wooden and carbon diaphragms as well, although he was not aware of it.

tinned ones, and extending them across the box, so as to reduce the intervening space to be bridged by the carbon particles, and by using fragments of proper microphonic carbon in lieu of Blyth's cinders, a transmitter of which no one need be ashamed is formed. The carbon may be much coarser than the powder described by Hunnings, but in view of Hughes's prior publication there can be no risk in using even the finest powder in a wooden box, no part of which partakes more of the nature of a diaphragm than another. As we have seen that Edison was before Hunnings with

metal diaphragms, and Hughes and Blyth were before him with conducting matter in the form of powder and fragments of carbon, the most Hunnings can claim is a combination of the two, and he is, in fact, modest enough to so limit himself.

BLAKE (NO. 229, JANUARY 20TH, 1879). This is the next secondary patent in order of date. Blake's claims are five in number.

Claim 1 is for his method of holding a diaphragm by means of springs.

Claim 2 is for a spring carrying one of the microphone contacts, the other contact being carried by a second spring or fixed direct to the diaphragm.

Claim 3 is for Blake's peculiar form of adjusting lever.

Claim 4 is for the combination of two contacts, each carried by a spring.

Claim 5 is for the addition of a yielding weight to one of the springs, for the purpose of resisting the movement of the diaphragm and of modifying by its inertia the variation of pressure.

This need incommode nobody, since a diaphragm fastened at its edges as described by Edison is practically as efficient.

It is difficult, in face of Edison's Fig. 10, to imagine wherein this differs from Edison's plan, which, omitting the superfluous second spring, could be described in the same words.

Of course Blake is quite entitled to this. The form of adjusting screw shown by Edison in his Fig. 10 is not a very good one, but others could be devised without infringing Blake's. Edison's plan of one contact on a spring and the other on the diaphragm is practically as good.

This has a strong resemblance to the device described by Hughes to the Physical Society (Nature, June 27th, 1878): "The upper contact of a microphone should have its inertia supplemented by a balanced weight. This inertia I find to keep necessary the contact unbroken by powerful vibrations. No spring can supply the required inertia. But such weight is not really

a

necessary.

In fact, a transmitter made up to Edison's Fig. 10, but with only one spring and one pair of contacts, which could both be of hard carbon in lieu of Edison's plumbago and platinum, speaks at least as well as the Blake, and with such a transmitter, Fig. 2, Blake could not interfere. It would be unkind to an old acquaintance like Blake to hint anything about "colourable imitations," but there is certainly a family likeness between half of Edison's Fig. 10 (see Fig. 1), and the essential features of the Blake, a similarity accentuated by the coincidence that both inventors use platinum for one of their surfaces.

CROSSLEY (No. 412, FEBRUARY 1ST, 1879).

The last of the secondary patents to which importance is popularly attached is that of Crossley. It is a legal dictum that the contents of the provisional and final specifications of a patent must agree in substance. If they do not, or if matter is introduced into the final that is not foreshadowed in the provisional, then the patent is invalid, or, at least, the matter not so foreshadowed cannot be claimed. With the best intentions in the world, I must confess my inability to detect any novelty in Crossley's provisional or any resemblance between his provisional and final. The provisional is very short, and foreshadows an invention (!) consisting of nothing more nor less than "an ordinary microphone" (Crossley's own words) mounted on a parchment or other suitable diaphragm in conjunction with a battery and induction coil. Reading the provisional by itself, one would imagine that Mr. Crossley had lodged it under the impression that the use of an induction coil with a microphone was novel and with the design of protecting that combination.

But in the final it is stated (page 3, lines 26 to 28 and

56) that the induction coil is not necessary, only desirable. So the coil, not being a necessary part of the invention, must be deleted from the provisional, and then what remains? Nothing more than "an ordinary microphone" mounted on a parchment or other suitable diaphragm. But the process of elimination can be carried further, for in the final "an ordinary microphone" is defined as having only one pencil and two surfaces touching each other, to which," Mr. Crossley wisely adds, "I lay no claim." Take away this disowned ordinary microphone from the provisional, and what remains? Clearly, a parchment or other suitable diaphragm; an appliance not altogether unknown to Reiss in the early sixties. But in the final, the term "compound microphone" is introduced, and defined as a microphone having three, four, or more pencils, and six, eight, or more surfaces touching each other. The figures show compound microphones of Crossley's well-known form; but the claim is not for this form alone, but broadly for microphones having three, four, or more pencils, and six, eight, or more surfaces. Putting aside for the moment the want of agreement between the provisional and the final, I do not see how such a claim can be sustained; for Hughes, in his paper to the Physical Society, June 8, 1878 (Nature, June 27, 1878), nearly eight months prior to Crossley's patent, said: "A man's voice requires four surfaces of pine charcoal, six of willow, eight of boxwood, and ten of gas carbon." In another paper (Nature, May 16, 1878) Hughes said: "The effect was improved by building up the nails, log-hut fashion, into a square configuration, using 10 or 20 nails. A piece of steel watch chain acted well." Mr. F. J. M. Page, in a letter to Nature, May 30, 1878, speaks of three pieces of gas carbon in circuit with the primary of an induction coil and a Daniell cell.

These instances (and I could adduce others) of prior publication respecting multiple contacts are sufficient to destroy any particular claim to such contacts on Crossley's part. Even when arranged in his own special and highly meritorious form, the want of novelty in his provisional, and the startling disagreement between the provisional and final, would render interference on his part hopeless. Beyond all this, it should be borne in mind that an efficient surfaces, and to this, in any form, Crossley could not even transmitter can be made with only two pencils and four pretend a claim.

Mr. Crossley may, however, truly retort that although his patent may not have been drafted by a committee of Queen's counsel and patent agents, it was nevertheless very much to the purpose, since the innocent United Telephone Company gave him £17,500 for it! Crossley can certainly claim the laugh, if nothing else.

To sum up, for the reasons set forth, I believe that the following transmitters may legally be used after July 30: 1. All forms described by Edison in his No. 2,909, substituting, if desired, hard carbon for plumbago, platinum,

etc.

with diaphragm secured round its edges, with one contact 2. A transmitter, resembling Blake's in general form, but fixed on the diaphragm and with some form of adjusting lever other than Blake's, being practically Edison's Fig. 10. The details of such a transmitter, which contains nothing that was not anticipated by Edison, except the hard carbon contacts, which were anticipated by Hughes, are shown in Fig. 2.

3. All forms described by Hughes in his various papers. 4. Crossley's and analogous forms. 5. Blyth's.

6. Berliner's (No. 1,786, of 1884). A good transmitter, having contacts kept in position by gravity alone. Patent has lapsed.

Of these, Nos. 1, 2, 3, 5, and 6 could not be challenged without the challengers laying themselves open to an action for vexatious interference. No. 4 is safe for those who are not to be frightened by bluff, since there was absolutely no novelty of any description in Crossley's provisional, and his final claims something else. The following three would probably have to be defended if used, for, in spite of Hunnings having claimed only metallic or metal-covered diaphragms for his combination, they might be held as mere variations for the purposes of evasion:

7. Marr's. 8. Moseley's. 9. Berthon's.

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