rule designed by me for facilitating calculations respecting incandescence lamps. Mr. Bottone there suggests, with great confidence of statement, that my rule differs in no essential respect from one previously designed by Mr. John Innes, and for the sale of which he appears to be the agent. Allow me to state that previously to reading your note I had never heard of the name of Mr. John Innes in connection with any slide rule, and was in complete ignorance that he had designed one. Furthermore, on referring to the somewhat rough sketch given in the English Mechanic of July 27th, 1888, I find that the differences between my design and his are considerable. My object was to produce the very simplest form of mechanical calculator for performing glow-lamp calculations, and nothing else, and hence free from every complication due to the presence of other scales. His aim, according to his own statement, seems to have been to include all kinds of calculations about horse-power, copper deposited per hour, &c., &c., and the eleven scales in his rule render it considerably more complicated than do the four identical scales on mine. If the object of a slide rule is to perform a multiplicity of calculations the well known rules of Gravet and Boucher are adequate to do all these things, and much more. My experience, however, is that in the factory nothing can be too simple, and my purpose was to produce a slide rule for use there with as little complication about it as possible, and not as much.

There are other differences of detail into which I need not enter; suffice it to say in reply to Mr. Bottone :

1. That I was not in any way indebted for my ideas to the rule designed by Mr. Innes, and did not know of its existence. The notion of it occurred to me certainly before July, 1888.

2. That my rule and his are not the same in design, and not entirely the same in purpose.

3. That so far from describing the rule in the ipsissima verba of Mr. Innes, there is not one single paragraph which is the same in the five succinct instructions which are appended to my rule, and the short and very sketchy description which accompanies the design given in the English Mechanic.

In conclusion, since writing the above, I have found that in 1882 Profs. Ayrton and Perry described (see "Journal Soc. Tel. Engineers," Vol. XI., p. 277) an electric light calculator which was a circular slide rule, so that neither I nor Mr. Bottone need contend for priority, although I deem it desirable to place on record a counter-statement to his very confident assertion as to the " source from which the idea of the slide rule was originally derived."

Electrical Execution.

J. A. Fleming.

I wish to express my thanks for the fair and able article upon electrical execution in your issue of August 30th. As a contrast I inclose a clipping from the New York Sun, in which correspondence, stolen from my desk during my absence from the city, has been distorted and combined in a way designed to injure me, my signature being boldly forged to the letters alleged to be written by me. This article was preceded and followed by violent editorials personally attacking me, all of which bear the ear-marks of a certain alternating current company-for instance, the Thomson-Houston Company, the largest user of the alternating current in this country, is called a continuous-current " company. My offence seems to be that I proved the alternating current to be deadly when certain interested persons claimed that it was harmless; that when required by the State of New York to furnish execution apparatus I chose that which had killed dozens of innocent men, and purchased it of a company which had it for sale; and that I would not believe that twice two made six; and organised a competitive test of the Westinghouse alternating system, which is "guaranteed to give 50 per cent. more light per lb. of fuel" than any other, against the Thomson

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[SEPTEMBER 27, 1889.

Houston apparatus, and tried to get the United States and Edison systems into the test. All of these facts were known to the State authorities and to most of the electric light fraternity months ago, as I issued in April the enclosed circulars and distributed them widely. Notwithstanding which some of the American electrical papers published the Sun's attacks without coming to get the truth of the matter. Since the publication of the Sun's article the alternating current has had four more victims J. Kemmerle, fruit dealer, who touched an incandescent lamp while standing on a wet sidewalk at Pueblo, Colo., on August 29th; D. A. Henry, Superintendent East River Electric Light Company, killed September 2nd by touching primary wires; H. P. Ferry, lineman, who at Buffalo, N.Y., fell upon insulated wires carrying the primary current on September 5th; and a telephone lineman a day or two ago at St. Louis, Mo., whe made a ground connection with the Westinghouse system. It is evident that these deaths and many others were caused by confidence in the reckless statements concerning the safety of this current. A Westinghouse company operating in this city calls itself the Safety Electric Light Company. I prefer to be the subject of purchased newspaper abuse than to be the millionaire whose apparatus has killed fifteen or twenty innocent men, but who nevertheless states over his own signature that "pressures exceeding 1,000 volts (alternating current) can be withstood by persons in ordinary health without experiencing any permanent inconvenience." Harold P. Brown.

Electric Traction.

The misstatements in the letter of Mr. A. J. Jarman compel me to ask for the insertion of a reply upon 3 subject which has, I am afraid, little interest to anyone but those directly concerned.

Firstly, the truck or trolley for carrying cells was not invented or designed by Mr. Jarman, and has never been claimed by him until now. He had neither truck nor plan, for the simple reason that the cells could not be withdrawn endwise.

Secondly, he states that upon my appeal the Attorney-General compelled me to insert a dis claimer. Now, he knows as well as I do my counsel offered to insert the very words now printed in my specification, and I fail to see how it affects my patent. I have never claimed two armatures on one shaft, and it is a matter of indifference to me whether I mount them on one shaft or two.

Mr. Jarman gives you an extract from the Comptroller's decision, respecting which the Attorney-General said: "1 think that the Comptroller has gone too far in this case."

I am prepared to admit I gained a large part of my knowledge while with Mr. Jarman, and it was upon the principle" that from failures improvements spring:" and as he had little else but failures during that period, it stands to reason I had a grand field to make improvements, which when offered to him were ridiculed.

I am quite satisfied with the matter as it now stands, and I regret I have neither the time, the inclination, nor the ink-slinging ability to go further into the matter with him, until he compels me, by direful threats, to do so. But if any of your readers take sufficient interest in the system to call by appointment I shall be only too glad to show it to them.

ELECTRIC TRACTION.

WHEN is that good time coming when electric traction will take firm root in our large English cities? Periodically we are called upon to take a trial trip upon an electrically-propelled car constructed under the patents of some promising system, and almost invariably the experimental runs are so successfully performed that one concludes, after an examination of the machinery, that there exists no obstacle whatever to the immediate employment of these horseless vehicles. In spite of the fact that experience has shown them to be quite trustworthy so far as their daily running is concerned, and inasmuch as statistics from America have shown that electric traction is the cheapest method of propelling tramcars, yet we seem to be no nearer to the ultimate object of our desires than when Radcliffe Ward made his preliminary experiments some years ago at Leytonstone. In this, as in most new enterprises, England will be about the last to take it up; but when that happy day arrives it is to be hoped that the pioneers of an industry which has such a great future will be amply rewarded for their weary years of waiting. We have recently learned that a well-known company in London has received an order for electric cars to be used in Australia to the extent of £45,000, and that the Thomson-Houston people in America have just added to their already large contracts another of ten times the sum just named. Still, we are desirous of seeing electric traction thrive nearer home, and there is just the hope that the London Tramways Company may shortly introduce Jarman's system upon their South London lines.

It was only on Tuesday night last that we made a series of lengthy trips on the experimental car of Mr. Jarman, which has now been in intermittent use for nearly three years, and which still appears to be capable of withstanding any amount of hard usage. The distances covered were the greatest we have hitherto been privileged to travel in this manner, and the road was not in a state which might be called

perfect, yet everything which we could think of to try the efficiency of the car was performed over and over again with ease, and we were much pleased with the results of our nocturnal expedition which ran into several hours. Our readers are aware that Mr. Jarman employs a double armature motor and accumulators; therefore it is not necessary to enter into any details concerning the electrical features of the car. A new vehicle is just on the point of completion which will be much lighter than that which has had to bear the brunt of the last three years' labour, and this, it is hoped, will shortly be running. Mr. Jarman believes that before long he will have six cars-the minimum number which he thinks it possible to work below the cost of horse traction-in daily operation, and we only hope that his supporters will carry him through to a triumphant issue. If he can imbue them and the directors of the Tramway Company with a little of his own enthusiasm for awhile we shall see electric locomotion at last making a fair start in the metropolis, and when one line can show a saving on its present mode of working, others will be only too glad to follow.

LEGISLATION WANTED.

WE have been taught to believe that the days of miracles no longer exist, but if the extraordinary statements which are going the round of the daily press respecting the doings of Professor Edward Moross, exofficer in the Army, are allowed to go uncontroverted or unexplained, the public will believe that we have once again in our midst a miracle worker. The name of the gentleman is familiar to those of our readers who but a short time since followed the case of Moross v. Parkes, and he now presents himself before the Metropolitan public as the pre-eminent and renowned medical electrician. We had hoped that the unwary would have been misled by but one of these gentry, but there are now two Richmonds in the field, and the new comer bids fair to oust the Oxford Street practitioner from the

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proud position he has occupied for so long. The Professor's system is unique, unrivalled. It differs from all others, and no longer will sufferers need doctors or medicine. The apparatus with which these wonderful results are to be obtained consist mainly of an electrical chair and carpet. The pre-eminent medical electrician. does not deal in electropathic belts, in which he does not place any faith, or things of such a low order, but like his congener, Harness, he is not unmindful of the poor, for the carpet has been specially designed to meet the wants, of the working classes and those patients whose circumstances are not such as to enable them to come under the Professor's treatment, or to defray the cost of the electric chair. We have already alluded to a lecture given by Moross at St. James's Hall, on June 12th last, and we had imagined that the cool reception which his pretensions received at the hands of a certain section of the daily press would have kept him in comparative obscurity, but the genus medical electrician is irrepressible, and so it will continue until it comes within the meshes of the law; and we really think that some Member of Parliament should be induced to bring this kind of quackery before the notice of the House.

Instead of the nuisance showing any signs of abatement it is rapidly on the increase, and this is not to be wondered at when we consider the monetary success which has attended the operations of some of the now notorious vendors of so-called medical appliances. A man need only possess assurance and audacity enough to set himself up in commodious and handsomely furnished rooms, advertise himself freely as a medical electrician, and he at once reaps a rich harvest. Could not Sir Lyon Playfair, Sir John Lubbock, Dr. Cameron, or even Mr. Labouchere take up this gross abuse of electrical science and bring all rank impostors to task? Many a matter is continually cropping up in Parliament which does not affect the country in anything like such a degree as do these wholesale raids upon the pockets of the public at large. Mr. De Watteville might try to exert his influence through the medium of the medical Press upon his fellow practitioners, and we should be glad to aid in any movement of a practical nature to rid the community of such pests as certain of these so-called medical electricians.

Omnia mutantur, nos et mutamur in illis. This maxim is very applicable just now to our contemporary Industries, the London editor of which, our esteemed friend Mr. Gisbert Kapp, has, we regret to say, resigned his position, and has this week severed his connection with that journal. Those persons who have watched the progress of our contemporary since its commencement a little over three years ago, must have noticed the excellent manner in which the electrical department especially has been conducted under the able editorship of Mr. Kapp. This gentleman always tried to be first in the field in noticing new inventions, &c., and if by chance a contemporary anticipated his intended notice, he would decline to have anything to do in the matter, a policy which is not, however, always beneficial to the interests of readers of technical

[OCTOBER 4, 1889.

papers. Mr. Kapp has brought Industries to a high standard of efficiency, and the sole reason of his resigning is, we are informed, due to the fact of some unpleasantness having arisen with the proprietary. We believe Mr. Kapp intends to start in business as an electrical engineer, and we wish him every success in his old sphere. His successor in electrical matters will be Mr. J. Swinburne, who, we imagine, will now disassociate himself from all business matters which might influence his editorial opinion.

A SHORT time ago we announced that steps were shortly to be taken with a view to the Houses of Parliament being lighted throughout by electricity, and that probably tenders would be asked for the lighting. A portion of the Houses is already, and has been for some time, electrically illuminated, and it is surprising that this has not become general. Then, again, there are the various Government establishments, the majority of which are not yet supplied with electric lights. The post offices, generally speaking, are badly served, and one characteristic of them is that the desks allotted to the public for writing telegrams, filling up money and postal orders, &c., are exceedingly poorly lighted. Whether this is another example of red tapeism or not we cannot say, but it is high time that a change took place. In this connection the English Government might take a leaf out of the book of the Indian Government, which is about to introduce electric lighting in the Viceregal residence in Calcutta, and also in that of the LieutenantGovernor. Several companies are competing for the contract, but the tenders sent in show a higher cost than was expected. One of the difficulties met with is the fact that the light is only required a few months in every year, and this has led to the suggestion that accumulators should be employed. This, however, is impossible, owing to there being no central station in the immediate neighbourhood or district. A direct system of transmission is generally advocated, and will doubtless be carried into effect. Everybody in the Indian towns seem to favour the introduction of the electric light, but unless the schemes are worked out in an economical manner very little good will result.

IT has been accepted as an acknowledged fact that lead-covered cables, when placed underground in creosoted wooden troughs, undergo a rapid deterioration of the lead sheathing owing to the metal being converted into a carbonate, but closer research tends to show that this destruction need not necessarily take place. Close observation of creosoted conduits and lead-covered cables, laid at various times since 1884, apparently prove that the destructive agent usually present in freshly crecsoted wood disappears almost entirely after a few years. A cable was laid upwards of two years ago in a conduit constructed in 1884, and at this date there is but very slight trace of action on its surface, while part of the same cable laid in an 1888 conduit shows considerable scale of carbonate of lead after one year's exposure. Parts of the same cable placed in other conduits about a year after their construction show but little damage. One cable laid in 1885 is only slightly affected, and it is not anticipated that any further deterioration will take place. Some experiments, to test the effect of time and ventilation on creosoted wood, were carried out by placing cables covered with an alloy of tin and lead in boxes made

of creosoted wood, one box made of wood creosoted more than two years back, and another more recently impregnated. These boxes were sealed up and opened after a lapse of three months. The samples in the old wood box were barely touched, while the samples in the newer one were thickly covered on the sides and top with what is chemically known as phenolate. Either phenol, a volatile, gas, or acetic acid in combination with carbonic acid gas will attack lead and reduce it to a carbonate. If no acetic acid is present in the wood, and the phenol be evaporated by some means or another, there should be no more damage done to lead cables in creosoted troughs than if they were run in conduits of other materials; but means should be taken to freely ventilate the troughs, not only to protect the cables, but also to guard against accumulations of explosive gas. Under these conditions plain lead sheathing would prove as efficient as that made of the tin alloy, the durability of which latter covering can hardly be accepted as assured.

SEVERAL enterprising American Tramway Companies, not content with having altered their systems from horse to cable traction, are about to contract for the conversion of the cable system into one worked by electricity.

FROM Chattanooga comes the interesting account of a neat little bit of Company promotion. The patentee of an electric light system erected a small installation there, and then sold his plant, with his State rights, to a local company for $8,000. Having obtained his money he left town, so did the money, and so apparently did the electric light, for that has been out ever since. The shareholders are anxiously awaiting the promoter's return.

A MAN-OF-WAR of the present day may be anything but a thing of beauty, but it has its countervailing advantage in being naturally protected from lightning strokes. Far different was it in olden days. In 50 years over 200 ships of the British Navy were struck by lightning, while from 1810 to 1815 some 48 vessels were more or less damaged. In one squadron of 13 ships, blockading, or cruising off the French Mediterranean coast, five were struck during one night with a heavy loss to their crews. Many casualties occurred in the Navy through the explosion of powder magazines.

A DR. WATSON in the last century proposed to protect British warships by a copper conductor, and he was requested by the then First Lord of the Admiralty to devise a suitable method for so doing. His lightning conductor consisted of links of copper made into a chain, which was made fast to a strong rope and attached to an iron rod on the royal truck, whence it was taken to the sea below. This conductor was supplied packed in a box, to be applied when it was deemed necessary. There was some difficulty in erecting this chain, and very often by the time it was fixed the storm was over. It was never popular, and in consequence it was seldom used. It was not without danger to fix the conductor in working order, several sailors in an American manof-war having been killed while in the performance of their duty of taking the chain aloft. This mode of protection fell into disuse.

THE well-known scientist, Sir William Snow Harris, then took up the question of protecting ships from lightning, and by every means in his power urged on the authorities to provide permanent conductors for our warships. He was successful in his endeavours, and our navy has experienced comparatively little damage from lightning since then.

APART from the modern vessels being protected by their construction, or by special provisions for the purpose, it would seem that lightning does not play as destructive a part as it did 40 or 50 years ago, as even those ships unprovided with conductors have suffered less damage than a smaller number of ships experienced formerly. Not that modern vessels are exempt, but they seem to be struck in a manner which causes fewer fatal accidents, and in some cases, even, the effects of a lightning flash have borne so little trace of their origin that they have been credited to the wilful act of someone on board.

THE recent adoption by the Post Office of an arrangement by which telephonic communication in certain districts will be available to those of the general public who are not subscribers to a telephonic exchange, will, if generally extended, but hasten the acquisition of the whole telephonic system by the State. That this change is bound to come sooner or later there can, we think, be but little doubt. The adoption of the sixpenny rate, forced as it was on the Postal Department regardless of the extra expense to the country which it involved, has no doubt to some extent retarded the buying up of the telephonic companies' interests, as there is always a tendency for the Government to wriggle out of any scheme which involves extra expense, unless public opinion, by a division in Parliament, forces their hands. The public will, we believe, welcome a telephonic system worked;and controlled by the Postal Telegraph Department, as it means a good service and good apparatus; the high rates of subscription, if at the present scale, would, however, decidedly be grumbled at, and probably pressure would have to be brought to bear to make some material reduction in this respect. The acquisition by the State of the telephonic system in London would eventually mean the abolition of the overhouse wires, an improvement which would be hailed by those of an aesthetic turn of mind, with great pleasure, even if the absence of interruption from fires, gales, and snowstorms, is not taken into consideration.

IT seems time that something practical was done with reference to the electrical unit question; we hear a great deal of talk and the suggestion of a large number of new units, chiefly mechanical, which it cannot honestly be said any one has felt the want of, but good solid work in the form of practically determining the value of the units which are in constant use has been only done spasmodically by a number of isolated individuals. What is being done in the matter of the proposed Standardising laboratory? We should also like to know when the report of the Institute of Electrical Engineers' committee on electrical nomenclature is likely to be issued, although in face of the fact that the whole matter seems to be forgotten by those who are most interested, it would seem as if the report might be postponed indefinitely without much loss to the community.

INDUCTION AND OTHER THINGS.

MACAULAY used to be inspired by the book he was geriewing, and write an original essay on the same In one case, for instance, he began by saying be was not going to mention the book under review in the rest of the article. We propose to write this essay Macanlay's best style, but Dr. Fleming's recent book is far too important a work to be treated in at all

-band manner. We will, however, digress into ers which are not in the book, but are merely zgested by it.

Dr. Fleming's work, though not otherwise suggestive of Macaulay's style, is far too comprehensive for its title. It is really an encyclopædia article on "induction" of the most thorough and complete kind, and might have been meant for insertion in a very large electrical lexicon.

The conventional ideas about electricity and electrical induction are undergoing such rapid changes just now, that it is very difficult for people with little time at their disposal, or small mathematical attainments, to follow them. Dr. Fleming's first volume therefore appears just at the right time.

There is confusion in the use of the terms "lines of force" and "lines of induction" in many books. We would suggest that the terms should be kept quite distinct. In statics, if the attraction between two exceedingly small bodies is to be calculated, you think of one of them, and then imagine straight lines drawn from it in all directions. To find its attraction on the second body, you find how many lines per square centimetre there are at the second body due to the first body, and multiply by the mass of the second. If preferred, the second body can be considered to develop a star of lines, and the number per square centimetre so produced by it at the first body, multiplied by its mass again gives the mutual attraction. The force here varies as the number of lines per sq. cm., so these lines may well be called lines of force. These lines of force are straight. Suppose, however, we consider the bodies to radiate their lines at the same time; the lines will intersect one another all through space. If these sets of lines are now replaced by lines representing their components, we get a system of curved lines, which are crowded together where they enter or come out of the bodies. To get the force acting on one of the bodies it is necessary to take the surface integral of the component of the square of the number of lines per sq. cm. over it. These are therefore not lines of force but of induction. In the example taken, if the lines are both taken as positive, the force will be repulsion; so one set of lines of induction must be taken as going into the body, not out of it; as if that body was negatively charged while the other is positive. We thus get a clear distinction between lines of force and lines of induction. We might, perhaps, consider lines of force to belong to volume integrals and action at a distance, and lines of induction to surface integrals and action through a medium; but it is unnecessary to go into this here. Lines of magnetic induction are thus not lines of force at all, though they are frequently so-called, and to find the force due to them a surface integral of their squares has to be taken. To find the force on a unit pole in a unit field, the unit field is sometimes taken as being produced by a unit pole at unit distance, but sometimes it is put into a field induced by a current, or by a magnet with two poles; that is to say, it is supposed to be put into a field of unit induction, and it is not supposed to interfere with the direction or distribution of the induction. Here we have a mixture of the line of force and the line of induction methods; we take a volume integral of the product of the induction and magnetic density of the loose pole. To be consistent, we might imagine the induction disturbed by the in

"The Alternate Current Transformer in Theory and Practice." Vol. I. The Electrician Printing and Publishing Company, Limited. 1889.

sertion of the loose pole, and then take the surface integral of the square to get the force. It is not for a moment pretended that such a method would be mathematically convenient, but that it might be more consistent physically. Take, now, the case of a conductor carrying a current inserted in a magnetic field. To get the force by the mixed method, a volume integral of the product of the current density, and the component of the induction at right angles to the direction of the current turned through a right angle is taken. To get the same result by a surface integral, the field may be taken as disturbed by the current, and, as the force is at right angles to the direction of the induction, such curves as those of equal potential might be taken. We do not bring forward these suggestions as practical, or particularly valuable, but as showing how a confusion of lines of force and lines of induction might be avoided. If the notion of loose poles, acting on each other at a distance by means of lines of force, instead of through a medium by lines of induction, is discarded, we eliminate the idea of magnetic moment, and of magnetisation; and it might be of great advantage to get rid of magnetisation altogether. What is magnetisation? Nobody exactly knows. Take an electro-magnet. It is treated as if it were not a solid lump, but were made up of a number of minute magnets with space between them. The magnetisation of each little magnet is due to the direct action at a distance of every element of current, and of all the rest of the particles taken one end at a time. It is just as difficult to conceive the little magnet as the large one, but it is very common to try to avoid such difficulties by referring them to ultimate particles, or to little imaginary things instead of big real ones. Of course, the particles are supposed to be uniformly magnetised. There is also supposed to be induction in the spaces due to the action of the current elements and the ends, and the two together make up the total induction. Sometimes the particles are considered already magnetised, and the magnetising, or magnetic force of the exciting current is supposed to turn them against friction of some sort. Instead of magnetisable particles we may take the Ampère-Weber theory. Suppose the particles are not magnetisable, but are perfect conductors in a belt round their equators. If an exciting current is started it will induce surface currents in these particles, and they will try to arrange themselves at right angles to the exciting current. The action is like that of the disc in Dr. Fleming's alternating current galvanometer-which, by the way, he has omitted from his book-or of the closed armature coil of a Tesla motor. If the particles cannot turn freely the body is thus diamagnetic. If perfectly free to turn the body is neither diamagnetic, nor paramagnetic, like a gas. If the particles have currents initially they will try to arrange themselves parallel to the exciting current, like the moving coil of a dynamometer. If the initial currents are small the particles will first try to arrange themselves parallel, but the current will be decreased by the exciting current, and it may finally be reversed, when they will try to move back again.

The great beauty of the molecular current theory of magnetisation is that it cuts its own throat, if we may use such a vulgar expression in its connection without disrespect to so recondite a phenomenon. There is then no magnetisation at any point in the whole electromagnet; and we have only to deal with magnetic force, or, if we prefer it, induction, and may discard notions of magnetisation altogether. In addition to magnetisation being merely an idea, we have the difficulty that in some bodies the susceptibility is zero, so that you may apply as much magnetic force as desired without magnetising it at all. But some bodies have a negative susceptibility. They begin by not being magnetised at all; and when you apply magnetic force they get still less magnetised. This is an idea of great beauty. On the other hand, if you think of induction and permeability these difficulties are avoided.

Magnetisation appears therefore to be either an abstraction adopted for mathematical convenience, but having no physical meaning, or a quantity chosen to