Experimental Researches in Electricity, Volume 1

The date of a scientific paper containing any pretensions to discovery is frequently a matter of serious importance, and it is a great misfortune that there are many most valuable communications, essential to the history and progress of science, with respect to which this point cannot now be ascertained. This arises from the circumstance of the papers having no dates attached to them individually, and of the journals in which they appear having such as are inaccurate, i.e. dates of a period earlier than that of publication. I may refer to the note at the end of the First Series, as an illustration of the kind of confusion thus produced. These circumstances have induced me to affix a date at the top of every other page, and I have thought myself justified in using that placed by the Secretary of the Royal Society on each paper as it was received. An author has no right, perhaps, to claim an earlier one, unless it has received confirmation by some public act or officer.

Before concluding these lines I would beg leave to make a reference or two; first, to my own Papers on Electro-magnetic Rotations in the Quarterly Journal of Science, 1822. xii. 74. 186. 283. 416, and also to my Letter on Magneto-electric Induction in the Annales de Chimie, li. p. 404. These might, as to the matter, very properly have appeared in this volume, but they would have interfered with it as a simple reprint of the "Experimental Researches" of the Philosophical Transactions.

Then I wish to refer, in relation to the Fourth Series on a new law of Electric Conduction, to Franklin's experiments on the non-conduction of ice, which have been very properly separated and set forth by Professor Bache (Journal of the Franklin Institute, 1836. xvii. 183.). These, which I did not at all remember as to the extent of the effect, though they in no way anticipate the expression of the law I state as to the general effect of liquefaction on electrolytes, still should never be forgotten when speaking of that law as applicable to the case of water.

There are two papers which I am anxious to refer to, as corrections or criticisms of parts of the Experimental Researches. The first of these is one by Jacobi (Philosophical Magazine, 1838. xiii. 401.), relative to the possible production of a spark on completing the junction of the two metals of a single pair of plates (915.). It is an excellent paper, and though I have not repeated the experiments, the description of them convinces me that I must have been in error. The second is by that excellent philosopher, Marianini (Memoria della Societa Italiana di Modena, xxi. 205), and is a critical and experimental examination of Series viii, and of the question whether metallic contact is or is not productive of a part of the electricity of the voltaic pile. I see no reason as yet to alter the opinion I have given; but the paper is so very valuable, comes to the question so directly, and the point itself is of such great importance, that I intend at the first opportunity renewing the inquiry, and, if I can, rendering the proofs either on the one side or the other undeniable to all.

Other parts of these researches have received the honour of critical attention from various philosophers, to all of whom I am obliged, and some of whose corrections I have acknowledged in the foot notes. There are, no doubt, occasions on which I have not felt the force of the remarks, but time and the progress of science will best settle such cases; and, although I cannot honestly say that I wish to be found in error, yet I do fervently hope that the progress of science in the hands of its many zealous present cultivators will be such, as by giving us new and other developments, and laws more and more general in their applications, will even make me think that what is written and illustrated in these experimental researches, belongs to the by-gone parts of science.

MICHAEL FARADAY.

Royal Institution, March, 1839.

CONTENTS.

Par. Series I. S. 1. Induction of electric currents 6 S. 2. Evolution of electricity from magnetism 27 S. 3. New electrical state or condition of matter 60 S. 4. Explication of Arago's magnetic phenomena 81 Series II. S. 5. Terrestrial magneto-electric induction 140 S. 6. Force and direction of magneto-electric induction generally 193 Series III. S. 7. Identity of electricities from different sources 265 ---- ---- i Voltaic electricity 268 ---- ---- ii Ordinary electricity 284 ---- ---- iii Magneto-electricity 343 ---- ---- iv Thermo-electricity 349 ---- ---- v Animal electricity 351 S. 8. Relation by measure of common and voltaic electricity 361 ---- Note respecting Ampere's inductive results after 379 Series IV. S. 9. New law of electric conduction 380 S. 10. On conducting power generally 418 Series V. S. 11. Electro-chemical decomposition 450 ---- P 1. New conditions of electro-chemical decomposition 453 ---- P 2. Influence of water in such decomposition 472 ---- P 3. Theory of electro-chemical decomposition 477 Series VI. S. 12. Power of platina, &c. to induce combination 564 Series VII. S. 11.* Electro-chemical decomposition continued (nomenclature) 661 ---- P 4. Some general conditions of Electro-chemical decomposition 669 ---- P 5. Volta-electrometer 704 ---- P 6. Primary and secondary results 742 ---- P 7. Definite nature and extent of electro-chemical forces 783 ---- ---- Electro-chemical equivalents 822 S. 13. Absolute quantity of Electricity in the molecules of matter 852 Series VIII. S. 14. Electricity of the voltaic pile 875 ---- P 1. Simple voltaic circles 875 ---- P 2. Electrolytic intensity 966 ---- P 3. Associated voltaic circles; or battery 989 ---- P 4. Resistance of an electrolyte to decomposition 1007 ---- P 5. General remarks on the active battery 1034 Series IX. S. 15. Induction of a current on itself 1048 ---- Inductive action of currents generally 1101 Series X. S. 16. Improved voltaic battery 1119 S. 17. Practical results with the voltaic battery 1136 Series XI. S. 18. On static induction 1161 ---- P 1. Induction an action of contiguous particles 1161 ---- P 2. Absolute charge of matter 1169 ---- P 3. Electrometer and inductive apparatus 1179 ---- P 4. Induction in curved lines 1215 ---- ---- Conduction by glass, lac, sulphur, &c. 1283 ---- P 5. Specific inductive capacity 1252 ---- P 6. General results as to the nature of induction 1295 ---- ---- Differential inductometer 1307 Series XII. ---- P 7. Conduction or conductive discharge 1320 ---- P 8. Electrolytic discharge 1343 ---- P 9. Disruptive discharge 1359 ---- ---- ---- Insulation 1362 ---- ---- ---- as spark 1406 ---- ---- ---- as brush 1425 ---- ---- ---- positive and negative 1465 Series XIII. ---- ---- ---- as glow 1526 ---- ---- ---- dark 1544 ---- P 10. Convection; or carrying discharge 1562 ---- P 11. Relation of a vacuum to electrical phenomena 1613 S. 19. Nature of the electric current 1617 ---- ---- its transverse forces 1653 Series XIV. S. 20. Nature of the electric force or forces 1667 S. 21. Relation of the electric and magnetic forces 1709 S. 22. Note on electrical excitation 1737 Index Notes

EXPERIMENTAL RESEARCHES IN ELECTRICITY.

FIRST SERIES.

S 1. On the Induction of Electric Currents. S 2. On the Evolution of Electricity from Magnetism. S 3. On a new Electrical Condition of Matter. S 4. On Arago's Magnetic Phenomena.

[Read November 24, 1831.]

1. The power which electricity of tension possesses of causing an opposite electrical state in its vicinity has been expressed by the general term Induction; which, as it has been received into scientific language, may also, with propriety, be used in the same general sense to express the power which electrical currents may possess of inducing any particular state upon matter in their immediate neighbourhood, otherwise indifferent. It is with this meaning that I purpose using it in the present paper.

2. Certain effects of the induction of electrical currents have already been recognised and described: as those of magnetization; Ampere's experiments of bringing a copper disc near to a flat spiral; his repetition with electro-magnets of Arago's extraordinary experiments, and perhaps a few others. Still it appeared unlikely that these could be all the effects which induction by currents could produce; especially as, upon dispensing with iron, almost the whole of them disappear, whilst yet an infinity of bodies, exhibiting definite phenomena of induction with electricity of tension, still remain to be acted upon by the induction of electricity in motion.

3. Further: Whether Ampere's beautiful theory were adopted, or any other, or whatever reservation were mentally made, still it appeared very extraordinary, that as every electric current was accompanied by a corresponding intensity of magnetic action at right angles to the current, good conductors of electricity, when placed within the sphere of this action, should not have any current induced through them, or some sensible effect produced equivalent in force to such a current.

4. These considerations, with their consequence, the hope of obtaining electricity from ordinary magnetism, have stimulated me at various times to investigate experimentally the inductive effect of electric currents. I lately arrived at positive results; and not only had my hopes fulfilled, but obtained a key which appeared to me to open out a full explanation of Arago's magnetic phenomena, and also to discover a new state, which may probably have great influence in some of the most important effects of electric currents.

5. These results I purpose describing, not as they were obtained, but in such a manner as to give the most concise view of the whole.

S 1. Induction of Electric Currents.

6. About twenty-six feet of copper wire one twentieth of an inch in diameter were wound round a cylinder of wood as a helix, the different spires of which were prevented from touching by a thin interposed twine. This helix was covered with calico, and then a second wire applied in the same manner. In this way twelve helices were superposed, each containing an average length of wire of twenty-seven feet, and all in the same direction. The first, third, fifth, seventh, ninth, and eleventh of these helices were connected at their extremities end to end, so as to form one helix; the others were connected in a similar manner; and thus two principal helices were produced, closely interposed, having the same direction, not touching anywhere, and each containing one hundred and fifty-five feet in length of wire.

7. One of these helices was connected with a galvanometer, the other with a voltaic battery of ten pairs of plates four inches square, with double coppers and well charged; yet not the slightest sensible reflection of the galvanometer-needle could be observed.

8. A similar compound helix, consisting of six lengths of copper and six of soft iron wire, was constructed. The resulting iron helix contained two hundred and fourteen feet of wire, the resulting copper helix two hundred and eight feet; but whether the current from the trough was passed through the copper or the iron helix, no effect upon the other could be perceived at the galvanometer.