f> Sir IL Daiy on the Magnetic Phfcnomena [Jan. 



. All the wires were kept as cool as possible by immersion 

 !i! a basin of water.* 



ji made a number of experiments of the same kind, but the 

 results were never precisely alike, though they sometimes 

 approached very near each other. When the batteries were 

 l>ii;hly charged, so that the intensity of the electricity was higher, 

 the ditt'erences were less between the best and worst conductors, 

 and they were greater when the charge was extremely feeble. 

 Thus, with a fresh charge of about one part of nitric acid, and 

 iiine parts of water, wires of -.-V-^ of silver and platinum five 

 inches long, discharged respectively the electricity of 30, and 

 ^ftven double plates. 



Finding that when different portions of the same wire plunged 

 in a non-conducting fluid were connected with different parts of 

 the same battery equally charged, their conducting powers 

 l^peared in the inverse ratio of their lengths ; so, when six 

 ♦aphes of wire of platinum of -r\-^ discharged the electricity of 

 10 double plates, o inches discharged that of 20, l-i- inch that of 

 40, aixl 1 inch that of 60 ; it occurred to me that the conducting 

 powers of the different metals might be more easily compared 

 in this way, as it would be possible to make the contacts in less 

 time than when the batteries were changed, and consequently 

 wcith less variation in the charge. 



Operating in this way, I ascertained that in discharging the 

 electricity of 60 pairs of plates, 1 inch of platinum was equal to 

 about 6 inches of silver, to 5^^ inches of copper, to 4 of gold, to 

 3*8 of lead, to about -j-"^ of palladium, and -^^- of iron, all the 

 n^etals being in a cooling fluid medium. 



I found, as might have been expected, that the conducting 

 powerof a wire for electricity, in batteries of the size and num- 

 ber of plates just described, was nearly directly as the mass ; 

 thus, when a certain length of wire of platinum discharged one 

 battery,t the same length of wire of six times the weight dis- 

 charged six batteries ; and the effect was exactly the same, 

 piX)vided the wires were kept cool, whether the mass was a 

 single wire, or composed of six of the smaller wires in contact 

 with each other. This result alone showed, that surface had no 

 relation to conducting power, at least for electricity of this 

 kind, and it was more distinctly proved by a direct experiment^ 

 equal lengths and equal weights of wire of platinum, one roundy 

 and one flattened by being passed transversely through rollers 

 80, as to have six or seven times the surface, were compared as 

 to conducting powers : the flattened wire was the best conduc* 

 tor in air from its greater cooling powers, but in water no diffew 

 ence could be perceived between them. 



• Water is so bad ^ conductor, that in expe«iaicnts of this kind, its effects nij^y be 

 neglected altoj»ether; and these effects were equal in all the experiments. 

 •f A foot of this wire weighed 113 grains; a foot of the other, 6*7 grain*. 



