immersed in pure water and in oocygenated water. 355 



A pair of iron plates thus formed was 

 taken to the banks of a small stream in 

 Cheshire, called the Grange brook ; one 

 plate was placed in a current of mode- 

 rate velocity, where the water poured 

 through the interstices of the coils ; the 

 other plate was dropped into still water 

 in a convenient place at the edge. In 

 both plates the solderings at A pro- 

 jected above the surface and were kept 

 dry. 



i When copper wire poles were placed 

 in a decomposing cell filled with sulphate 

 of copper solution, and connected with 

 the galvanic couple formed of two pieces 

 of iron (fig. 2), distinct evidence of the precipitation of me- 

 tallic copper on the wire connected with the plate in still 

 water, was observed after an hour's action, temperature 45°. 

 One of the iron plates was now removed to a cell filled with 

 water, and associated with a platinum plate, the arrangements 

 for precipitating metallic copper remaining as before. With 

 the temperature at 42°, the depositing of the metal did not 

 proceed so actively as it had done with an iron plate in a cur- 

 rent of water for a platinode. 



When the decomposing cell was filled with a solution of Sul- 

 phate of zinc, and zinc wire poles supplied, after three hours' 

 action, temperature 46°, the wire in connexion with the iron 

 plate in still water showed, with the aid of a lens, a distinct 

 deposit of metallic zinc. Repeating this experiment with an 

 iron and platinum couple in still water, the metallic deposit of 

 zinc was again obtained, temperature 46°, the rate of action in 

 both experiments being, as near as I could judge, the same. 



The inference from these results is, that a piece of bright 

 iron placed in a current of water performs the office of a piece 

 of platinum, as well as the latter metal does when excited by 

 still water. 



The quantities of metal precipitated during two or three 

 hours' action of these oxygen absorbing batteries is in no 

 case sufficient to give results by weight. I have tried experi- 

 ments of one week each, but the changes in the level of the 

 stream and other sources of derangement, made me prefer 

 trials of two or three hours each, where 'there is no difficulty 

 in detecting any decided change in the rate of action. 



The Grange brook is supplied with water almost wholly by 

 the drainage of a rather poor clay soil, reposing on the new 

 red sandstone formation of the district* 



2 A 2 



