the contractile organs of animals, as the heart and other muscles, it seems to me to be a legitimate inference from all which has been said, that divergence is a vital action, and in every sense analogous to the contractility or irritability of the animal system.

In a future communication I shall endeavour to extend this analogy, by showing that the motions of plants may be traced to this same property, as those of animals are to irritability*. Shrewsbury, Oct. 6, 1834.

XXVII. On a new Phenomenon in Magneto-Electricity. By Mr. EDWARD M. CLARKE.

To the Editors of the Philosophical Magazine and Journal. Gentlemen,

HAVING for some time past been engaged in the manu

facture of the new magnetic electrical machines, in their completion and in the subsequent trials of their action I have observed a phænomenon which I have not anywhere seen an account of. I shall describe the effect as briefly as I can: in order to do this I have furnished a diagram of part of the machine.

[* We are indebted to a medical friend for the remark, that the phænomenon described by Dr. Johnson most closely resembles the contraction of the ligamentum nucha, by which the head of animals is retracted after death, and which Bichat attributes to vital contractility, which he regards as a distinct property.-EDIT.]

Third Series. Vol. 6. No. 33. March 1835.

Ꮓ

A represents the commencement of the collecting wire coils in connexion with the rotating pointed piece B, dipping into and leaving the mercury C simultaneously with the movement of the collecting coils on the rotating armature of the magnet. A' represents the terminations of the collecting coils in connexion with the rotating disk B', which is always in the mercury C'; D, a copper wire in contact with the mercury C, the point of which is in. contact with the wire that carries the pointed piece B. The director wires, E E', are represented as in connexion with each portion of mercury, and of course in connexion with the collecting wire coils. On holding the directors E E' in the wetted hands, a slight continuous thrilling sensation is felt; but if they are brought into contact and then separated, on the moment of their separation a powerful instantaneous shock is felt passing through the arms. The same effect is produced if you remove the pointed piece B. A continued scintillation and combustion of steel wire and surfaces, or of other metals, can be produced by substituting them for the directors E E'.

39, Charles Street, Parliament Street, January 13, 1835.

EDWARD M. CLARKE.

XXVIII. Note relative to the Form of the Fibres of Cotton. By JAMES THOMSON, Esq., F.R.S.

IN the first volume of the Bulletin de la Société Industrielle

de Mulhausen, is a memoir by M. Josué Heilman, entitled "Observations microscopiques sur la forme, la finesse, et la force des filamens de Coton," in which he ascribes to the fibres of cotton the precisely same form as that given to them in the drawing of Mr. Bauer, dated February 11, 1822, which accompanies my paper on Mummy Cloth, Lond. & Edin. Phil. Mag. vol. v. p. 355.

Mr. Heilman's "Observations" are accompanied by a drawing by Mr. Edward Koechlin, of these fibres. Whoever will take the trouble to compare the two drawings will detect internal evidence of the one being derived from the other. Mr. Heilman's paper being published in 1828, and mine in 1834, renders some explanation necessary.

In 1822 or 1823, Mr. Edward Koechlin was in England, and during a visit he made to Primrose, he saw Mr. Bauer's drawing, and requested permission to copy it, which was granted. It is from this drawing and Mr. Koechlin's communication that Mr. Heilman's "Observations microscopiques" are derived. The paltry fraud of appropriating to

* Communicated by the Author.

himself the observations of others without acknowledgement, might have passed unnoticed by me for ever, had not the friends of Mr. Bauer deemed this explanation necessary. Primrose, January 31, 1835.

XXIX. Experimental Researches in Electricity.-Eighth Series. By MICHAEL FARADAY, D.C.L. F.R.S. Fullerian Prof. Chem. Royal Institution, Corr. Memb. Royal and Imp. Acadd. of Sciences, Paris, Petersburgh, Florence, Copenhagen, Berlin, &c. &c.

[Continued from p. 133.]

935. IN order to put the equal and similar action of acid and alkali to stronger proof, arrangements were made as in (Plate I.) fig. 8.; the glass vessel A contained dilute sulphuric acid, the corresponding glass vessel B solution of potassa, P P was a plate of platina dipping into both solutions, and ZZ two plates of amalgamated zinc connected with a delicate galvanometer. When these were plunged at the same time into the two vessels, there was generally a first feeble effect, and that in favour of the alkali, i. e. the electric current tended to pass through the vessels in the direction of the arrow, being the reverse direction of that which the acid in A would have produced alone but the effect instantly ceased, and the action of the plates in the vessels was so equal, that, being contrary, because of the contrary position of the plates, no permanent current resulted.

936. Occasionally a zinc plate was substituted for the plate PP, and platina plates for the plates Z Z; but this caused no difference in the results: nor did a further change of the middle plate to copper produce any alteration.

937. As the opposition of electro-motive pairs of plates produces results other than those due to the mere difference of their independent actions (1011. 1045.), I devised another form of apparatus, in which the action of acid and alkali might be more directly compared. A cylindrical glass cup, about two inches deep within, an inch in internal diameter, and at least a quarter of an inch in thickness, was cut down the middle into two halves, fig. 9. A broad brass ring, larger in diameter than the cup, was supplied with a screw at one side; so that when the two halves of the cup were within the ring, and the screw was made to press tightly against the glass, the cup held any fluid put into it. Bibulous paper of different degrees of permeability was then cut into pieces of such a size as to be easily introduced between the loosened halves of the

cup, and served when the latter were tightened again to form a porous division down the middle of the cup, sufficient to keep any two fluids on opposite sides of the paper from mingling, except very slowly, and yet allowing them to act freely as one electrolyte. The two spaces thus produced I will call the cells A and B, fig. 10. This instrument I have found of most general application in the investigation of the relation of fluids and metals amongst themselves and to each other. By combining its use with that of the galvanometer, it is easy to ascertain the relation of one metal with two fluids, or of two metals with one fluid, or of two metals and two fluids upon each other.

938. Dilute sulphuric acid, sp. gr. 1-25, was put into the cell A, and a strong solution of caustic potassa into the cell B; they mingled slowly through the paper, and at last a thick crust of sulphate of potassa formed on the side of the paper next to the alkali. A plate of clean platina was put into each cell and connected with a delicate galvanometer, but no electric current could be observed. Hence the contact of acid with one platina plate, and [of] alkali with the other, was unable to produce a current; nor was the combination of the acid with the alkali more effectual (925.).

939. When one of the platina plates was removed and a zinc plate substituted, either amalgamated or not, a strong electric current was produced. But, whether the zinc were in the acid whilst the platina was in the alkali, or whether the reverse order were chosen, the electric current was always from the zinc through the electrolyte to the platina, and back through the galvanometer to the zinc, the current seeming to be strongest when the zinc was in the alkali and the platina in the acid.

940. In these experiments, therefore, the acid seems to have no power over the alkali, but to be rather inferior to it in force. Hence there is no reason to suppose that the combination of the oxide formed with the acid around it has any direct influence in producing the electricity evolved, the whole of which appears to be due to the oxidation of the metal (919.).

941. The alkali, in fact, is superior to the acid in bringing a metal into what is called the positive state; for if plates of the same metal, as zinc, tin, lead, or copper, be used both in the acid or alkali, the electric current is from the alkali across the cell to the acid, and back through the galvanometer to the alkali, as Sir Humphry Davy formerly stated*. This current is so

* Elements of Chemical Philosophy, p. 149; or Philosophical Transactions, 1826, p. 403. [or Phil. Mag. and Annals, N.S., vol. i. p. 101.]

powerful, that if amalgamated zinc, or tin, or lead be used, the metal in the acid evolves hydrogen the moment it is placed in communication with that in the alkali,-not from any direct action of the acid upon it, for if the contact be broken the action ceases, but because it is powerfully negative with regard to the metal in the alkali.

942. The superiority of alkali is further proved by this, that if zinc and tin be used, or tin and lead, whichever metal is put into the alkali becomes positive, that in the acid being negative. Whichever is in the alkali is oxidized, whilst that in the acid remains in the metallic state, as far as the electric current is concerned.

943. When sulphuretted solutions are used (930.) in illustration of the assertion, that it is the chemical action of the metal and one of the ions of the associated electrolyte that produces all the electricity of the voltaic circuit, the proofs are still the same. Thus, as Sir Humphry Davy* has shown, if iron and copper be plunged into dilute acid, the current is from the iron through the liquid to the copper: in solution of potassa it is in the same direction, but in solution of sulphuret of potassa it is reversed. In the first two cases it is oxygen which combines with the iron, in the latter sulphur which combines with the copper, that produces the electric current; but both of these are ions, existing as such in the electrolyte, which is at the same moment suffering decomposition; and, what is more, both of these are anions, for they leave the electrolytes at their anodes, and act just as chlorine, iodine, or any other anion would act which might have been previously chosen as that which should be used to throw the voltaic circle into activity.

944. The following experiments complete the series of proofs of the origin of the electricity in the voltaic pile. A fluid amalgam of potassium, containing not more than a hundredth of that metal, was put into pure water, and connected through the galvanometer with a plate of platina in the same water. There was immediately an electric current from the amalgam through the electrolyte to the platina. This must have been due to the oxidation only of the metal, for there was neither acid nor alkali to combine with, or in any way act on, the body produced.

945. Again, a plate of clean lead and a plate of platina were put into pure water. pure water. There was immediately a powerful current produced from the lead through the fluid to the platina : it was even intense enough to decompose solution of the iodide

* Elements of Chemical Philosophy, p. 148.