Editorial.

PROF. MORSE'S DEFENCE AGAINST PROF. HENRY'S ATTACK.

It is a matter deeply to be regretted, when it becomes necessary for one to defend himself against the unjust aspersions of a fellow-man, but more particularly so in the case given in the present number of the "Telegraph Companion." Although we most heartily concur in the utterance of every word expressed by Prof. Morse, we are, nevertheless, pained to feel, that it is a necessary infliction of a just punishment, and one, too, that is administered with the most moderate feeling, upon the part of Prof. Morse, towards one who has done so much to his injury.

After reading the exposé of Prof. Morse, of what Prof. Henry has done and what he claims to have done, and his incomprehensible course, no one, it occurs to us, can consider the conduct of Prof. Henry as other than evidence of hallucination. Prof. Henry has been regarded as a distinguished man in American science. He has occupied stations of honor in our institutions of learning, and his energy and presumed talents have given him a name of distinction throughout his own land, and have also won for him the admiration of the savans of Europe. The promulgation of the facts, by Prof. Morse, will startle those who have accorded to Prof. Henry unmeasured praise. The question as to what he has really discovered, will naturally arise in the minds of all. It now seems that the whole of his claims to discoveries in science, are to be considered with doubt. Prof. Morse proves his statements so grossly incorrect, that in future no dependence can be placed upon the statistics or assertions put forth by Prof. Henry. The defence of Prof. Morse is sustained by evidence which cannot be questioned, and the tone and words used by him, in repelling such an unjust attack, are certainly marked with as much candor and moderation, as can be desired by the most fastidious reader.

We have not the room in the present number to give a review of the questions under consideration, and so ably set forth by Prof. Morse. In the next number of the "Companion," we may have something to say on the subject.

SHAFFNER'S

TELEGRAPH COMPANION,

DEVOTED TO THE SCIENCE AND ART OF THE

MORSE AMERICAN TELEGRAPH.

VOL. II.

APRIL, 1855.

Art. I.-ELECTRIC INDUCTION.

BY PROFESSOR M. FARADAY, F. R. S.

[Presented to the Royal Institution of Great Britain.]

No. 2.

ON ELECTRIC INDUCTION-ASSOCIATED CASES OF CURRENT AND STATIC

EFFECTS.

CERTAIN phenomena that have presented themselves in the course of the extraordinary expansion which the works of the Electric Telegraph Company have undergone, appeared to me to offer remarkable illustrations of some fundamental principles of Electricity, and strong confirmation of the truthfulness of the view which I put forth sixteen years ago, respecting the mutually dependent nature of induction, conduction, and insulation, (Experimental Researches, 1318, &c.) I am deeply indebted to the Company; to the Gutta Percha works, and to Mr. Latimer Clarke, for the facts; and also for the opportunity both of seeing and showing them well.

Copper wire is perfectly covered with gutta percha at the Company's works, the metal and the covering being in every part regular and concentric. The covered wire is usually made into half mile lengths, the necessary junctions being effected by twisting or binding, and ultimately, soldering; after which the place is covered with fine gutta percha, in such a manner as to make the coating as perfect there as elsewhere: the perfection of the whole operation is finally tried in the following striking manner, by Mr. Statham, the manager of the works. The half mile coils are suspended from the sides of barges floating in a canal, so that the coils are immersed in the water whilst the two ends of each coil rise into the air: as many as 200 coils are thus immersed at once, and when their ends are connected in series, one great length of 100 miles of submerged wire is produced,

the two extremities of which can be brought into a room for experiment. An insulated voltaic battery of many pairs of zinc and copper, with dilute sulphuric acid, has one end connected with the earth, and the other, through a galvanometer, with either end of the submerged wire. Passing by the first effect, and continuing the contact, it is evident that the battery current can take advantage of the whole accumulated conduction or defective insulation in the 100 miles of gutta percha on the wire, and that whatever portion of electricity passes through to the water will be shown by the galvanometer. Now the battery is made one of intensity, in order to raise the character of the proof, and the galvanometer employed is of considerable delicacy; yet so high is the insulation, that the deflection is not more than 5°. As another test of the perfect state of the wire, when the two ends of the battery are connected with the two ends of the wire, there is a powerful current of electricity shown by a much coarser instrument; but when any one junction in the course of the 100 miles is separated, the current is stopped, and the leak or deficiency of insulation rendered as small as before. The perfection and condition of the wire may be judged of by these facts.

The 100 miles, by means of which I saw the phenomena, were thus good as to insulation. The copper wire was of an inch in diameter:-the covered wire was; some was a little less, being in diameter:-the gutta percha on the metal may therefore be considered as 0.1 of an inch in thickness. 100 miles of like covered wire in coils were heaped up on the floor of a dry warehouse and connected in one series, for comparison with that under water.

Consider now an insulated battery of 360 pairs of plates (4 x 3 inches) having one extremity to the earth; the water wire with both its insulated ends in the room, and a good earth discharge wire ready for the requisite communications:—when the free battery end was placed in contact with the water wire and then removed, and, afterwards, a person touching the earth discharge touched also the wire, he received a powerful shock. The shock was rather that of a voltaic than of a Leyden battery; it occupied time, and by quick tapping touches could be divided into numerous small shocks. I obtained as many as 40 sensible shocks from one charge of the wire. If time were allowed to intervene between the charge and discharge of the wire, the shock was less; but it was sensible after 2, 3, or 4 minutes, or even a longer period.

When, after the wire had been in contact with the battery, it was placed in contact with a Statham's fuze, it ignited the fuze

(or even 6 fuzes in succession) vividly :--it could ignite the fuze 3 or 4 seconds after separation from the battery. When, having been in contact with the battery, it was separated and placed in contact with a galvanometer, it affected the instrument very powerfully-it acted on it, though less powerfully, after the lapse of 4 or 5 minutes, and even affected it sensibly 20 or 30 minutes after it had been separated from the battery. When the insulated galvanometer was permanently attached to the end of the water wire, and the battery pole was brought in contact with the free end of the instrument, it was most instructive to see the great rush of electricity into the wire; yet after that was over, though the contact was continued, the deflection was not more than 50, so high was the insulation. Then separating the battery from the galvanometer, and touching the latter with the earth wire, it was just as striking to see the electricity rush out of the wire, holding for a time the magnet of the instrument in the reverse direction to that due to the ingress or charge.

These effects were produced equally well with either pole of the battery, or with either end of the wire; and whether the electric condition was conferred and withdrawn at the same end, or at the opposite ends of the 100 miles, made no difference in the results. An intensity battery was required, for reasons which will be very evident in the sequel. That employed was able to decompose only a very small quantity of water in a given time. A Grove's battery of 8 or 10 pair of plates, which would have far surpassed it in this respect, would have had scarcely a sensible power in affecting the wire.

When the 100 miles of wire in the air were experimented with in like manner, not the slightest signs of any of these effects were produced. There is reason, from principle, to believe that an infinitesimal result is obtainable, but as compared to the water wire the action was nothing. Yet the wire was equally well and better insulated, and as regarded a constant current, it was an equally good conductor. This point was ascertained, by attaching the end of the water wire to one galvanometer, and the end of the air wire to another like instrument; the two other ends of the wires were fastened together, and to the earth contact; the two free galvanometer ends were fastened together, and to the free pole of the battery; in this manner the current was divided between the air and water wires, but the galvanometers were affected to precisely the same amount. To make the result more certain, these instruments were changed one for the other, but the deviations were still alike: so that the two wires conducted with equal facility.

The cause of the first results is, upon consideration, evident

enough. In consequence of the perfection of the workmanship, a Leyden arrrangement is produced upon a large scale; the copper wire becomes charged statically with that electricity which the pole of the battery connected with it can supply;* it acts by induction through the gutta percha, (without which induction it could not itself become charged, Exp. Res. 1177,) producing the opposite state on the surface of the water touching the gutta percha, which forms the outer coating of this curious arrangement. The gutta percha across which the induction occurs, is only 0.1 of an inch thick, and the extent of the coating is enormous. The surface of the copper wire is nearly 8,300 square feet, and the surface of the outer coating of water is four times that amount, or 33,000 square feet. Hence the striking character of the results. The intensity of the static charge acquired is only equal to the intensity at the pole of the battery whence it is derived; but its quantity is enormous, because of the immense extent of the Leyden arrangement; and hence when the wire is separated from the battery and the charge employed, it has all the powers of a considerable voltaic current, and gives results which the best ordinary electric machines and Leyden arrangements cannot as yet approach.

That the air wire produces none of these effects is simply because there is no outer coating correspondent to the water, or only one so far removed as to allow of no sensible induction, and therefore the inner wire cannot become charged. In the air wire of the warehouse, the floor, walls, and ceiling of the place constituted the outer coating, and this was at a considera ble distance; and in any case could only affect the outside portions of the coils of wire. I understand that 100 miles of wire, stretched in a line through the air, so as to have its whole extent opposed to earth, is equally inefficient in showing the effects, and there it must be the distance of the inductric and inducteous surfaces (1483), combined with the lower specific inductive capacity of air, as compared with gutta percha, which causes the negative result. The phenomena altogether offer a beautiful case of the identity of static and dynamic electricity. The whole power of a considerable battery may in this way be worked off in separate portions, and measured out in units of static force, and yet be employed afterwards for any or every purpose of voltaic electricity.

I now proceed to further consequences of associated static and dynamic effects. Wires covered with gutta percha, and then inclosed in tubes of lead or of iron, or buried in the earth, or

* Davy, Elements of Chemical Philosophy, p. 154.