Current) and on the Intensities of Voltaic Arrangements. 107 



1842. Two plates of iron were immersed in a dilute solution 

 of sulphuric acid and then connected with the poles of a bat- 

 tery consisting of six large cells of Daniell in series. After 

 electrolysis had proceeded for a few minutes, I observed that 

 the needle of a galvanometer which was included in the cir- 

 cuit indicated by its unsteadiness a very great irregularity in 

 the electrical current. On connecting only one cell of the 

 battery with the iron electrodes, the electrolysis appeared to 

 be carried on with freedom and the needle was pretty steady. 



About the same time I made some experiments with elec- 

 trodes of copper immersed in a solution consisting of seven 

 parts of water and one part of strong oil of vitriol. In this 

 case the sudden jerking motion of the needle was not observed, 

 but it invariably happened that the current diminished very 

 rapidly during the first one or two minutes, and then began 

 to increase again, and continued to do so, until, after a certain 

 interval of time, it arrived nearly at the same degree of inten- 

 sity as was observed at first. I give the following as a fair 

 example selected out of a number of experiments which did 

 not differ much from one another. 



A vessel containing dilute sulphuric acid was divided into 

 two compartments by a diaphragm of animal membrane. In 

 each of these a bright plate of copper exposing a surface of 

 about ten square inches was immersed. The copper plates 

 were then connected with a battery consisting of six large cells 

 of Daniell in series, a galvanometer furnished with a thick 

 copper wire bent into a circle of a foot diameter being included 

 in the circuit. Immediately after the circuit was closed the 

 current was sufficiently powerful to deflect the needle to 69°. 

 Then, noting the position of the needle at the end of each 

 quarter of a minute, I observed the following deflections, viz. 

 68°, 60°, 55°, 10°, 20°, 30°, 35°, 41°, 43°. Turning these 

 deflections into quantities of electricity, it appears that in the 

 short space of one minute the voltaic current declined to ^ y th 

 of its first intensity, and that at the end of 1^' more it had 

 eight times the intensity that it had when at its lowest ebb. 



1 met with very curious results by using amalgamated zinc 

 as the positive electrode of a battery of six large cells. The 

 needle was pretty steady at first, but after a short time it 

 began to oscillate in the most capricious manner through an 

 arc of about 10°. Sometimes it would remain steady for a few 

 seconds, then it would suddenly spring forwards, and before I 

 had time to make it steady in its new position of equilibrium 

 it would move backwards again. 



It was natural enough to suppose that such extraordinary 

 irregularities of the current might be accompanied by a visible 

 change in the character of the electrode. And in this I was 



