10 



Mr. T. C. Porter. 



[Nov. 9, 



glass vessel, but not touching them. Two pieces of platinum foil, 

 about 3 inches long and f inch wide, hang at each end of the glass 

 vessel, facing the central strip on both its sides ; the central strip is 

 the cathode, on which the iron is deposited, the other two being the 

 anodes. The current having been switched on to the coils, and the 

 single Groves' cell used, to the electrodes, the iron solution is poured 

 in, till it reaches as high as the top of the pole pieces. After three 

 minutes there was a discoloration of the platinum from the very thin 

 film of iron formed upon it, and on testing this, by withdrawing it 

 from the solution and applying it edgeways to a rather heavy compass 

 needle, by no means delicately mounted, it was found to give distinct 

 evidence of polarity, the repulsion and attraction being most clearly 

 visible, and on tearing off a strip of the platinum along its base, and 

 drying it and balancing it on a fine sewing needle, it quickly set itself 

 in the magnetic meridian, and has continued to do so with apparently 

 equal activity ever since, although the film of iron must be exceedingly 

 thin. The main portion of the strip was replaced in the solution, and 

 the deposition of the iron continued, its polarity being tested from 

 time to time. Its magnetic intensity increased, though certainly at a 

 diminishing rate. Finally, when all the iron in the solution had been 

 deposited the platinum was taken out, washed with distilled water, the 

 part covered with iron torn off (so that it did not touch any other iron) 

 and put into dry air for preservation. It has remained a magnet ever 

 since, and as yet gives no sign of diminished intensity, though it has 

 been made to vibrate, and hit with a wooden rod repeatedly. 



The whole experiment has been repeated, with the same results.* If 

 during the deposition the platinum be reversed, side for side, after a 

 certain time the iron deposited shows no polarity, and after that its 

 polarity is reversed. Whether this is due to the reversal of polarity 

 in the molecules first deposited, as well as to the deposition upon 

 them of molecules having opposite jDolarity, or to the latter cause only, 

 the writer has not yet determined, nor has it been possible in this 

 paper to give measurements either of the magnetic intensities, or of 

 the thickness of the thinnest film of pure electrolytic iron which is. 

 capable of making its polarity felt; nor again is it yet possible to 

 say how long the polarity of these artificial magnets will continue. 

 Answers to these questions, by the very nature of the investigation, 

 must be left for a future communication. 



The solution from which the iron was deposited is constituted as 

 follows : — 



20 grammes FeSO^NH^SO^fLO, 

 64 grammes (NH 4 ) 2 C 2 4 .H 2 0. 

 Made up to 960 c.c. with distilled water. 



* The writer was unaware at the time that a similar experiment had been made 

 by Beetz, and quoted by Maxwell. 



