was in connection with like efforts to exhibit strikingly to his pupils in classes the principles of electro-magnetism, that he made his first contribution to a science which, if we count from Oersted's experiments as its beginning, was at this time six years old. Not much had been done with the subject in America, Henry says, in a paper read before the Albany Institute, Oct. 10, 1827:

"In a paper published in the Transactions of the Albany Institute, June, 1828, I described some modifications of apparatus intended to supply this deficiency of Mr. Sturgeon by introducing the spiral coil on the principle of the galvanic multiplier of Prof. Schweigger, and this I think is applicable in every case where strong magnets cannot be used. The coil is formed by covering copper wire, from

ment of Arts. Henry, after repeating all the experiments of Oersted, Ampere and others, was, from his own experimental investigations, enabled to exhibit to his classes all the illustrations of Sturgeon on a much larger scale; with weak magnets, if necessary, and with still less battery power. These striking results were obtained by a simple expedient. Look again at Schweigger's multiplier. [See figure] Henry recognized the principle involved, viz., that in coiling the wire of a galvanic circuit the strength of the electrical current is increased, and in every case where a single wire circuit had been employed, he used a manifold coil of wire. By means of this coil Schweigger's multiplier became in Henry's hands an instrument of much greater delicacy and power; and Henry was not only able to produce with it more striking effects than Sturgeon had produced, but an apparatus capable of exhibiting phenomena of which Sturgeon's instruments were incapable. Henry says in his paper: "Mr. Sturgeon's suite of apparatus, though superior to any other as far as it goes, does not however form a complete set; as indeed it is plain that his principle of strong magnets cannot be introduced into every article required and particularly in those intended to exhibit the action of the earth's magnetism on a galvanic current, or the operation of two conjunctive wires on each other. To form therefore a set of instruments, on a large scale, that will illustrate all the facts belonging to this science, with the least expense of galvanism, evidently requires some additional modification of apparatus and particularly in those cases in which powerful magnets cannot be applied."

too of an inch in diameter with silk; and in every case which will permit, instead of using a single conducting wire, the effect is multiplied by introducing a coil of this wire closely turned upon itself." "The following description will render my meaning sufficiently clear:

"Fig. 1, is an apparatus on the plan of the Multiplier, to show the deflection of a large magnetic needle. It consists of a coil of wire, A P, of an oblong form, about 10 inches in length and one and a half in width, with a small

galvanic element attached to each end; the coil is formed of about twenty turns of fine copper or brass wire wound with silk, to prevent contact, and the whole bound together so as to have the appearance of a single wire. The attachment of the zinc and copper is more plainly shown in Fig. 2, which represents a coil of only two turns of the wire; on the left side of the figure the plates are soldered directly to the ends of the wire of the coil; on the right, the plate of zinc z is attached to the part of the wire ending with copper on the other side, while the plate of copper on the right corresponds to the zinc on the left. By this arrangement we can instantly reverse the direction of the currents and deflect the needle either to the right or left, by merely holding a tumbler of acidulated water so as to immerse one or the other of the double plates into the fluid. The arrows at A and B, formed of two pieces of card, are intended to show the direction of the currents, and they should point in the course of the wires going from the copper. N S, is the needle, about nine and a half inches long, made by binding together several watch springs, touched separately, so as to form a compound magnet; at

A

FIGS. 3 AND 4.-HENRY'S MODIFICATIONS OF DE LA RIVE'S RING.

the end are two balls of pith, to show the movement of the needle more plainly. This instrument is complete in itself, and we receive the full effect of the instantaneous immersion of the galvanic element."

To show the advantage of the coil, take the little instrument called "De la Rive's ring," a modification of Ampere's

ingenious and delicate experiment for showing the directive action of the earth as a magnet on a galvanic current when its conductor is free to move. (See representation of it.) c and z are two plates, one of copper the other of zinc, connected by a loop of copper wire an inch or two in diameter and suspended in a little glass vase, containing acidulated water, which by the aid of a piece of cork D, floats in a vessel of water. The loop of wire is the circuit conveying the electric current c to z and -free to moveit must, if the magnetism of the earth is produced by electric currents circulating from East to West around it, arrange itself at right angles to the magnetic meridian, and so it does. The effect of this experiment was strikingly enhanced by Henry's method of suspending by a silk thread a large coil thirty inches in length bent into a parallelogram the ends of the wire projecting, and soldered each to a pair of galvanic plates. By placing a tumbler of acidulated water beneath the galvanic plates so that they could dip into it, he caused the coil to assume, after a few oscillations its equatorial position, transverse to the magnetic meridian. We give his own illustration and description of the arrangement.

"Fig. 3 represents a modification of De la Rive's ring on a large scale. A B, is a coil about nine inches by six, with a small cylinder of copper, enclosing another of zinc, without bottoms, soldered to its extremities, which end at c, the whole being suspended by a fibre of raw silk, so as to swing freely in a cup of acidulated water. When this apparatus is made sufficiently light it invariably places itself, after a few oscillations, at right angles to the magnetic meridian. w and E, are two pieces of card, with letters on them, to show which side of the coil will turn to the East or West; they may be properly placed by recollecting that the current from the copper to the zinc has a tendency to circulate in a direction contrary to that of the Bun."

By a similar arrangement of two coils of different sizes, the one suspended within the other, Ampere's fine discovery of the mutual action of two electric currents upon each other was as strikingly displayed. See Henry's figure and description of it, as follows:

Fig. 4 is designed to show the action of two conjunctive wires on each other: A B, is a thick multiplying coil, with galvanic plates attached, in the same manner as shown in Fig. 2; c d, is a lighter coil with a double cylinder, precisely similar to Fig. 3, and suspended within the other by a fibre of silk, passing through a glass tube a, the end of which is inserted into an opening b, in the upper side of A B; ef are two wires supporting the glass tube. When the cylinder g and the plates care placed in vessels of acidulated water, the inner coil will immediately arrange itself so that the currents in both coils will circulate the same way; if the vessel be removed from c, and D placed in the fluid, the coil c d will turn half way round and again settle, with the currents flowing in the same direction."

THE LIMITATIONS TO LONG DISTANCE TELEPHONY.-III.

BY

Tu Dubar

WE have now reached the third stated cause of the limitation to telephony and arrived at that cause which the engineer has always considered the vital one, that is, the absolute amount of decay in the amplitude of the vibration, caused by the capacity of the line, and increasing rapidly with the distance from the origin.

Again examining equation (4) we see that the effect of the capacity is first to increase the absolute value of the current at or near the origin, and, second, to cause a logarithmic decrement of its value with an increase in distance from the origin. The self-induction of the circuit causes first a decrease in the absolute value of the current at or near the origin, and, second, decreases the rate of decay caused by the capacity. Thus these two factors work in opposition and some relation must exist between them which will render I a maximum at the distant end.

Taking the first differential coefficient of I with respect to L, equating to zero and solving for L, will give us a value of L which on examination will be found to render I a maximum for any given set of conditions; that is, a definite length of line with a definite resistance, capacity and number of alternations.

C & t The term (R2 + L2 ∞3) -Lo has a maximum value of R and a minimum of 0 as L varies from 0 to infinity.

Designating it by R, we have

or L ∞ =

8

This equation shows us that if Lo has a finite value the 8 must exceed unity. Substituting the conC&R stants of the Chicago line we have

term

Ꮚ

8

THE WESTINGHOUSE COMPANY AND THE NIAGARA CONTRACT.

W*

print elsewhere in this issue an important communication from Mr. L. B. Stillwell, on behalf of the Westinghouse Co., which sheds a strong side light on the information embodied in Prof. Forbes' paper on the electrical features of the Niagara transmission plant. This communication, taken in connection with Prof. Forbes' own statements, would make it appear that so far as essential features are concerned, the promoters of the Niagara scheme deemed it wise to accept the advice of experienced constructors in preference to that of their consulting electrical engineer. And this brings us back to the old question of the relation between these two frequently antago nistic elements. The consulting electrical engineer's services have from the very outset been little availed of in this country, purchasers of electrical plants having in the large majority of cases left matters entirely in the hands of the contracting companies, which practice has, it must be admitted, given rise to but few conflicts. In the case of the work at Niagara, it would appear that the consulting electrical engineer, instead of confining himself to laying down the conditions and leaving to the contractors to devise the best methods of carrying out the specifications, actually entered into competition with them, with the result that might have been foreseen. According to Mr. Stillwell it would also seem that while the engineers of the Westinghouse Co., are in accord with Prof. Forbes on the selection of the methods adopted, they differ from him radically in the assumptions and reasoning which led them to advocate the final plans adopted.

It would be interesting to know the details of these differences and it is to be hoped that the electrical profession will not be kept in ignorance of them. For this reason it is perhaps a pity that Prof. Forbes' paper could not have been read and discussed on this side of the water also. Probably an early opportunity may be afforded by the Institute for such a timely discussion.

THE TESLA ELECTRICAL OSCILLATOR. WHILE Mr. Tesla has until the last year or two confined himself to purely electrical work, his most recent labors have been devoted to the solution of a mechanical problem intimately connected with the generation of electric currents, the outcome being his electrical oscillators, of which we describe two additional types in this week's issue. Aside from the numerous possibilities in other fields it would seem that if the "oscillator" fulfills the expectations of its inventor, it is destined to create little short of a revolution in our present methods of power generation and distribution. It must be confessed that in spite of the numerous obvious cases in which the application of motors to the driving of machines and line shafting would prove a gain over the present methods, and despite even the successful working of such plants, the conservative factory owner and machinist still looks with a doubtful glance at these innovations of the last ten years. But, if, as Mr. Tesla claims, he will be able to furnish electric current by means of his oscillator, at anything like one half the cost for fuel now required and with much simpler apparatus, the aspect becomes quite a

different one. Such an accomplishment would immediately appeal to every power user and would at once determine the direction of future methods of local power transmission. Indeed it might not be inapt to inquire here also into the probable effect of such an achievement on long distance electrical transmission. With the potentials which have been practically handled up to date, the size of conductors required has not permitted of the extension of power transmission plants utilizing water power, to the distances hoped for, although we note small but constant gains in this respect. With the initial source of energy in the shape of fuel reduced to one half the present cost, it would indeed require an exceptional set of conditions such for example, as those existing at Niagara or in regions far remote from fuel supply to make the utilization of water-powers worth considering for any considerable distance from the fall. Already the cost of water power even locally distributed has in numerous conspicuous instances proved less economical in competition with modern steam engines and a still further improvement in the latter added to the benefits to be derived from electric motors must still further tend to decrease the comparative margin of economy with water power. It seems strange indeed that a power available on the spot should not be able to compete in economy with another form of energy hauled frequently for a distance of hundreds of miles, but experience bears out the conclusions just stated. While the above remarks refer merely to power distribution they are equally applicable to the question of electric lighting and current distribution in general. From Mr. Tesla's observations before the recent meeting of the New York Electrical Society (see THE ELECTRICAL ENGINEER, Dec. 6 and 13, 1893) we infer that he has so far gone into the study of the methods he advocates that we shall not have to wait long for their practical realization.

ELECTRICITY AND THE STATE.

The reference to electricity in no less than three of the annual State papers of New York serves to indicate the important position assumed by this later source of energy. In the reports made to the Legislature by Gov. Flower, State Engineer Schenck and Superintendent of Public Works Hannan, reference is made to the contemplated employment of electricity as a motive power on the Erie Canal. The utterances of Mr. Schenck show him to be still somewhat skeptical as to the economy of the electric method as compared with the steam canal boat, the independence of which still appears to him as a most valuable feature. Judging from his other remarks it is evident that he has never heard of the dynamotor or motor transformer, nor of the work now actually being done by alternate current motors. On the other hand we are glad to note the intelligent grasp of the subject apparent in the brief reference to it contained in Mr. Hannan's report. This gentleman estimates that with a steam electric plant serving a stretch of 50 miles and operating 210 days in the year canal boats can be propelled for 10 cents per mile per boat, while still others estimate it at nearly one half this figure. If during the season when the canal is closed the power could be utilized in other ways the cost would be still further reduced. Mr. Hannan concludes from all this that the

claims to consideration for electric motive power on the canal are extremely well founded.

In the message of Governor Flower we note also a reference to the alleged increase of fires due to defective electric wiring, and a suggestion that persons installing such work be licensed by a competent board certifying to their fitness to carry it out properly. There is much to be commended in this plan which was for some time in operation in New England, but has unfortunately been allowed to lapse. Perhaps the trades unions themselves might find the easiest solution of this problem by allowing no one into their ranks who could not pass a rigid examination on wiring work. The statement that in the city of New York there are four times the number of fires that there are in the principal cities of Europe, accompanied by four times the destruction of property, may be true, but to cite it in the present connection without further qualification and without giving any figures or details whatever seems hardly fair. We know as a matter of fact that the actual figures on fires claimed to be of electrical origin do not in the least warrant any such assertion or inference and we are sorry indeed to see so unguarded a statement in a Governor's annual message. Last week we referred to a case within our personal knowledge where the insurance rate had been advanced nearly five fold-from 15 cents per $100 to 70. Inquiry elicits the fact that apartment buildings over a certain height have been re-rated on that basis. As we said last week, electricity has nothing to do with the case.

BI-METALLIC WIRES IN TELEPHONY.

EVER and anon the electrical public is brought face to face with statements and facts so at variance with past experience that they force themselves upon its attention and cause it to pause and ponder. The most recent example of a surprise of this nature is the discovery of the extraordinary properties of a composite wire for the transmission of telephonic currents and indeed for alternating currents in general. If we are to believe the statements printed on another page, from Mr. Wm. H. Eckert, whose long telegraphic and telephonic experience entitles his opinion to some weight, a composite wire embodies within itself properties which serve to overcome retardation whether due to electro-magnetic impedance or electro-static charge while at the same time it makes current largely independent of insulation. A result differing so widely from what we have been accustomed to deem as an inevitable accompaniments of all conductors will of course be accepted with great caution, but as the inventor bases his statements on actual experiments we must await further developments on this decidely interesting innovation with no small hopefulness.

An Injunction Against a "Gas" Lamp.

As we go to press, news reaches us by telegraph that Judge Shipman has to-day (Saturday) granted an injunction against the "Novak" incandescent lamp. The proceedings at Hartford were recently reported in our colAs we are still without the text of the decision, we are unable to pronounce on its scope. The lamp, it will be remembered, has a bromine atmosphere in the chamber. This was held by the defendants to exclude it from the scope of the Edison patent.

ums.