Prof. Faraday on Electro-dynamic Induction in Liquids. 267 



net. The eflfects were constant ; when the communicating wires 

 were crossed they again occurred, giving reverse actions at the 

 galvanometer. Further proof that they were due to currents 

 induced in the fluid helix was obtained by arranging one turn of 

 a copper wire round the iron core or keeper in the same direction 

 as that of the fluid helix, and using one pair of plates to excite 

 the magnet ; the induced current caused in the copper wire was 

 much stronger than that obtained with the fluid, but it was 

 always in the same dix'ection. 



After these experiments with the highly conducting solution, 

 the helix was removed, the dilute acid poured out, a stream of 

 water sent through the helix for some time, distilled water then 

 introduced and allowed to remain in it a while, which being 

 replaced by fresh distilled water, all things were restored to 

 their places as befoi'e, and thus a helix of pure water submitted 

 to experiment. The direct action of the magnet was the same 

 as in the first instance, but there was no appearance of a voltaic 

 current when the galvanometer communications were completed; 

 nor were there any signs of an induced current upon throwing 

 the magnet into and out of action. Pure water is too bad a 

 conductor to give any sensible efifects with a galvanometer and 

 magnet of this sensibility and power. 



1 then dismissed the helix, but, placing the keeper on the 

 magnetic poles, arranged a glass dish under it and filled the 

 dish with the same acid solution as before ; so that the liquid 

 formed a horizontal fluid disc 6 inches in diameter nearly, an 

 inch deep, and within 0*25 of an inch of the keeper ; two long, 

 clean, platina plates dipped into this acid on each side of the 

 keeper and parallel to it, and were at least 5 inches apart from 

 each other ; these were first connected together for a time that 

 any voltaic tendency might subside, and then arranged so as to 

 be united with the galvanometer when requisite, as before. Here 

 the induced currents were obtained as in the first instance, but 

 not with the same degree of strength. Their direction was 

 compared with that of the current induced in a single copper 

 wire passed between the fluid and the keepei', the magnet being 

 then excited by one cell, and was found to be the same. How- 

 ever, here the possibility exists of the current being in part or 

 altogether excited upon the portions of the wire conductors con- 

 nected with the platinum plates ; for as their ends tend to go 

 beneath the keeper, and so into the circuit of magnetic power 

 formed by it and the magnet, they are subject to the lines of 

 force in such a })Osition as to have the induced current formed in 

 them j and the induced current can obtain power enough to go 

 through liquid, as I showed in 1831. But as the helix experi- 

 ment is free from this objection, I do not doubt that a weak 

 induced current occurred in the fluid in the dish also. 



T2 



