An iron wire shows traces of remaining circular magnetism after the passage of a continuous current, reducing the following extra-currents 10 per cent.

Magnetising the wire, or subjecting it to mechanical vibrations, when used separately, produce no apparent change in its inductive capacity, but a remarkable change takes place if either of these is used in conjunction with a constant current. Let us pass a constant current and heat the wire to red heat, allowing it to cool with the current on; or, in place of heat, magnetise the wire; or, in place of magnetism, give the wire mechanical vibrations: the result of either of these being a strong internal circular magnetism, due, I believe, to the loosening of the magnetic molecules, allowing them to rotate with greater freedom under the influence of heat, mechanical vibrations, or magnetism. A wire thus treated has no longer its previous self-induction, which has fallen 60 per cent.; and as the circular magnetism becomes fixed when the vibrations cease, this molecular structure remains a constant as long as we employ intermittent currents in the same direction, but the structure disappears the instant a reverse current is sent; and this explains why we have more than double the amount of self-induction from reverse currents, as each reversal destroys any remaining magnetism due to the previous passage of the current.

If we compare the electro-motive force of self-induction on a given length of wire with the secondary currents generated in a second but independent circuit, we find that the self-induction is the most powerful, the secondary currents generated in a close independent copper wire being 20 per cent. less than its own wire. There is no difference between the self-induction of a current and the secondary currents; they are, as proved by Faraday, part of the same phenomenon, the self-induction being evidently due to the electro-magnetic reactions of the primary current, and as magnetism permeates space, the separation of the wires only serves to insulate the primary, but does not affect its magnetic, influence; and, as I have shown in the reactions of contiguous portions of the same current, so the magnetic reactions perpendicular to the axis of the current continue through the wire to

all surrounding wires; and if we call the currents in the independent wire secondary, they are still secondary whilst enclosed in the wire of the primary; and as the reaction will ever be the strongest in the axis of the current, so will these currents be necessarily stronger than those induced in independent wires. For this reason we should be able to obtain extra-currents of far higher electro-motive force than would be possible from a secondary wire of the same length.

It was my intention, on the reading of this paper, to demonstrate by practical experiments some remarkable properties of extra-currents of high electro-motive force; but I find that the subject and apparatus employed require a longer description than the limits of this paper allow. I must also leave aside for the present my experiments upon coils of different forms with cores of different metals. These, as well as other results obtained, indicate that there is a large field of useful research in many directions, each, however, requiring special studies according to the object we may have in view.

The record of numerous experiments, of which this paper is only an abstract, shows that the nature of the metal as well as its physical condition has an important influence upon the self-induction of an electric current, and by a study of the reactions produced by the contiguous portions of a current, and by application of the results, we may, as in the case of iron, transform an extremely slow conductor into one of the greatest rapidity; I therefore hope not only that these researches may be of interest from a scientific point of view, but that the results obtained may be of practical utility in some of the numerous applications of electricity.

Mr. C. E. SPAGNOLETTI: Gentlemen,-As Professor Perry is now present, I will take this opportunity of presenting to him the books for Dr. Oliver Lodge, and ask him to kindly convey to that gentleman the pleasant assurance that the meeting had at the proper period manifested its expression of approval of the award of the Council in regard to the presentation.

Professor PERRY: Will you allow me on my own behalf to thank you very much for having inconvenienced yourself so much

-26 ELECTION OF FOREIGN MEMBER, AND ASSOCIATES. [Jan. 28th,

as to delay the presentation on account of my enforced absence? I have just been lecturing at the London Institution. I should certainly have regretted it very much could I not have availed myself of the very great kindness of Dr. Lodge in asking me to represent him on this occasion, for it will be remembered by the Society that I took an active part in the discussion on his paper, to some parts of which I was as antagonistic as a man who loves England is antagonistic to what he thinks are English faults. In Dr. Lodge's name I thank you for the prize which you have awarded him, and I apologise for his not coming here to receive it himself. It is very difficult to leave college duties in Liverpool during term time. I think that he may have expected me to say that his paper was not worthy of the beautiful prize which has been awarded him, but I feel that I cannot say anything of the kind, because I feel that Dr. Lodge's paper is one of the best that has ever been read before the Society.

Mr. C. E. SPAGNOLETTI: I am afraid it is too late to-night to enter on the discussion of Professor Hughes's address. The meeting has been a very full one, and it must be very gratifying to him to see so many present, and I hope we shall have on the next occasion an equally good meeting for the discussion.

Upon the motion of Mr. SPAGNOLETTI, a hearty vote of thanks was accorded to Professor Hughes for his very valuable and interesting address, which he was requested to allow to be published in the Society's Journal, together with the discussion to which it may give rise.

A ballot for new members took place, at which the following -candidates were elected :

The meeting then adjourned until 11th February, 1886.

The One Hundred and Fifty-first Ordinary General Meeting of the Society was held at the Institution of Civil Engineers, 25, Great George Street, Westminster, on Thursday evening, February 11th, 1886-Professor D. E. HUGHES, F.R.S., President, in the Chair.

The minutes of the previous Meeting were read and confirmed. The names of new candidates for election into the Society were announced and ordered to be suspended.

The following transfers were announced as having been approved by the Council:

From the class of Associates to that of Members

The PRESIDENT: Before the discussion upon my paper is commenced, I think it right that I should vacate the chair, which in the meantime I would ask our senior Vice-President, Sir Charles Bright, to occupy.

Sir Charles Bright took the chair.

The PRESIDENT: I should like to point out a slight omissionof a word-in my paper, which has given rise to some little misunderstanding. The table of values represented by Fig. 2 in the paper represents the results upon wires of 30 centimètres in length; and the table is perfectly true, because I have verified it fifty or a hundred times for all variations of electro-motive force. The first idea that occurs to one on seeing the table is that the result is due to one experiment only; but repeated verification with varying electro-motive forces has proved that iron always comes out the highest. The only variation that can occur would be that with a lower current the curves would fall; but they would all fall, and would retain the same relative proportions. If

wires of great length are taken, the maximum would be found at larger diameters, as the increased resistance interferes with the result on the smaller wires; but the curves are true, as regards electro-motive force, for any length.

Sir CHARLES BRIGHT: The question we have before us is one of very great interest and importance. I do not know, among our members or friends who are here present, that anyone has paid more attention to the delicate effects of induction than Lord Rayleigh, and I shall be extremely pleased if he will favour us with his views upon the subject.

Lord RAYLEIGH: It is quite true, Sir, that I have given attention to some of the points touched upon by Professor Hughes in his very interesting paper; but that paper contains a good many other points which are quite new to me, as also, I suspect, to most others.

I observe that on the first page of the paper Professor Hughes does not employ the term "self-induction" in quite the same sense—or, at least, with quite the same definiteness-as it has been used by mathematicians, especially by Professor ClerkMaxwell, who used the term to express an absolutely definite quantity, dependent almost entirely upon the exact form of the electric circuit, and, with one exception, independent of the material of which the circuit is composed. The exception would, of course, relate to the use of the magnetic metals-iron principally-and also nickel and cobalt. If we exclude those metals, and if we ignore (which, I think, for such a purpose as this we might certainly do) the very feeble magnetism and diamagnetism of other metals, then we may say that the selfinduction is independent altogether of the material forming the conductor. There is, of course, another element entering into the matter, and that is the resistance of the circuit; that, again, is a perfectly distinct quantity. If we take the ratio of those two quantities, the coefficient of self-induction being on the electro-magnetic system of measurements a linear quantity, and the resistance being a quantity of the nature of velocity;if we divide the self-induction by the resistance, we get a quantity of the nature of time. [Explained on the board.]