1855.] 



OBSEllVATIONS ON ELECTRIC INDUCTlOxV, &c. 



299 



the resultant fibrous mass is worked up or macerated in the 

 usual rnaaner, for the production of a palp suitable for the use 

 of the paper-maker. This pulp may be used in the manufac- 

 ture of paper, either unmixed, or commingled with other 

 materials already in use for making paper. The routine of 

 manufacture into paper of the pulp, is similar to that pursued 

 with the ordinary rag pulp, or it may be varied, as the proper- 

 ties of the thistle may suggest. The thistle fibre being strong, 

 the paper made from it is of great tenacity, the fibres cohering 

 well together in the paper machine, and being worked up with 

 very little loss from washing away. The fibres are also of sjood 

 colour ; hence paper of a fair colour may be made from them 

 without bleaching, and if bleaching is resorted to, a very good 

 white colour is obtained at a slight expense. The mucilaginous 

 or gummy matter dislodged from the fibres may be collected 

 and applied in the manufacture of gum or glutinous matter, 

 or it may be otherwise rendered commercially valuable, so as 

 still further to economize the thistle manufacture. In apply- 

 ing the thistle plant to the manufacture of textile materials, 

 the fibres are primarily prepared in the manner already des- 

 cribed, and then subsequently treated according to the existing 

 textile processes — such, for instance, as arc adopted in the flax 

 manufacture, the thistle fibre being closely allied to the fibre 

 from the flax plant, as regards its general characteristics. 

 Being strong and of good staple, the thistle fibre is particularly 

 well suited for the spinning and weaving processes. 



Further Observations on associated cases, in Electric In- 

 duction, of Current and Static Effects. 



BV PKOF. FARADAY, D.C.t., F.R.S., *c.« 



Melloni, whose loss science must deeply feel, was engaged 

 in the latter part of his life in investigations relating to static 

 electricity, especially concerning induction, conduction, &c. 

 He desired, in reference to these and the results I had published 

 respecting the charge of, and conduction bj^, subterraneous and 

 subaqueous insulated wires, to know whether there was any 

 dilfereuee in the time of transmission through such wires, of 

 currents having greater or less intensity, i. c. of currents from 

 batteries of different numbers of plates. I applied to Mr. 

 Latimer Clai-k on the subject; and he with the same earnest- 

 ness as on the former occasion, sought and seized the opportu- 

 nity of making experiments of the like kind, and gave me the 

 results, which I sent to Melloni. The latter published them 

 with some observations in an Italian Journal (whose title is 

 not on the paper which he sent to me), and soon after he was 

 suddenly removed from us by death. As Mr. Clark's results 

 are not yet known in this country, I have thought that a brief 

 account of them would be valuable. His process records, by 

 the printing telegraph of Bain, the results obtained with 7G8 

 miles of copper wire covered with gutta pcrcha, and laid in 

 the ground in four lines between London and Manchester, so 

 connected that the beginning and the end of the whole length 

 was in London. The following are his words, dated May ol, 

 1854 :— 



" I have tried a few experiments on the relative velocities 

 of currents of different intensities, and I enclose j'ou some 

 strips of paper showing the results. I was unable to equalize 

 the deflexions of a galvanometer by currents of intensity with 

 small plates as compared with currents from a few large plates, 



* From the Lonrl., Edin. niifl Diih, Thilo?. Mnp. March, ]8>?. 



for no size of plate would make up for the deficiency in inten- 

 sity. I allude to the form of experiment suggested by Melloni ; 

 — -but I believe they will be of interest to him. 



" The experiments were made through 7GS miles of gutta 

 peroha wire, viz.: from London to Manchester and back again 

 twice, with our ordinary sulphate of copper batteries, plates 3 

 inches square, and with intensities varying from 31 cells to 

 sixteen times 31 cells, or 500 cells. 



"In the accompanying strips the upper line indicates the 

 time during which the current was sent, being made by a local 

 arrangement. 



" The second line (of dots) indicates time hy seconds, being 

 made by a pendulum vibrating seconds, and striking a light 

 spring at the centre of its arc of vibration. 



'i The third line indicates the time at which the current 

 appeared at (what we call) the distant end of the line, 768 

 miles off. 



" The fourth line merely shows the residual discharge from 

 the near end of the wire, which was allowed to communicate 

 with the earth as soon as the batteries were disconnected ; this 

 has no I'eferenco to the subject of our enquiries. 



" It will be seen by the t/iird line, that about two-thirds of 

 a second elapsed in every case before the current became 

 apparent at the distance of 768 miles, indicating a velocity of 

 about 1000 miles a second; but the most intere.sting part 

 appears to be, that this velocity is sensibli/ uniform for all 

 intensities from 31 cells to 500." 



Melloni has then given a copy of the records made when 31 

 pair and 500 pair of plates were employed ; unfortunately the 

 copy is inaccurate, since it makes the fourth line commence as 

 to time at the termination of the third, whereas it ought to 

 correspond with the termination of the first ;* also the "third 

 line on each does not thin 'olf as those upon the record do. 

 The following is a copy from other slips obtained at the same 

 time from the Bain's printing apparatus. Experiments with 

 62, 125, and 250 cells, save like results with those of 31 and 

 500 cells. 



31 cells. 



500 cells. 



After certain observations, which are mainly upon the man- 

 ner of the experiments, and the way in which practical 

 difficulties were avoided, Melloni says, " it appears, then, that 

 when the electric current possesses sufficient force to overcome 

 the sum of the resistance offered by a given conductor, what- 

 ever its length may be, an augmentation of its intensity ten or 

 twenty fold does not alter the velocity of its propagation. 

 This tact is in open contradiction with the general meaning 

 attributed to the denominations o£ (j nautili/ and inlensili/ ; 

 since the first compares the mass of electricity to that of a 

 fluid, and the second represents its elasticity or tendency to 

 motion. The equal velocity of currents of various tension 

 offers, on the contrary, a fine argument in favour of the opinion 

 of those who suppose the electric current to bo analogous to 

 the vibrations of air under the action of sonorous bodies. As 

 sounds, higher or lower in pitch, traverse in air the same space 

 in the same time, whatever be the length or the intensity of 



