Proceedings of the British Association. 101 



iron had been put into water, for, after the lapse of a couple of hours, 

 the polar wires were seen to be surrounded by light flakes of oxide of 

 iron. 3. A piece of iron being voltaically associated with zinc, was ex- 

 posed to the action of the atmosphere. Having left this voltaic pair for 

 some time to itself, the iron part of it appeared to be covered with a 

 thin layer of rust, and on comparing it with a piece of iron which had 

 also been placed within the atmosphere during the same space of time, 

 no evident difference could be detected between the states of the surfaces 

 of both pieces. 4. A piece of iron wire was connected with each of the 

 poles of a voltaic pile, without making the wires touch each other. 

 Being exposed to the action of the atmosphere under these circumstances, 

 both polar wires appeared, after some time, equally effected by rust, and 

 as much as another piece of iron which was not connected with a pile. 

 5. A piece of iron, being voltaically associated with zinc, was placed in 

 common water, so that both metals were deposited in the same vessel. 

 Although this voltaic pair has been kept in water for twelve months, the 

 iron part of it does not appear to be in the least degree oxidized, its 

 surface being perfectly brilliant. 6. A piece of iron wire was connected 

 with each of the poles of a pile, and each of these pieces made to plunge 

 into a separate vessel filled with common water, the vessels being 

 connected by means of a piece of platinum. That portion of the negative 

 polar wire which was immersed in the water did not rust at all, as long 

 as there was a current passing through the arrangement. 7. Copper 

 being intimately associated with zinc, and brought into an aqueous 

 solution of chloride of sodium (in such a manner that each of the metals 

 was plunged into a separate vessel), was soon chemically affected, — 

 provided that the vessels did not communicate with each other. 8. The 

 same experiment was made as in the preceding case, with the difference, 

 however, that both metals were plunged into the same vessel. Under 

 these circumstances, the copper piece was not in the least corroded by 

 the salt water, whatever the length of time was during which the metals 

 were immersed. 9. A piece of copper was connected with each of the 

 poles of a voltaic pile, and put into a vessel containing an aqueous 

 solution of common salt. Both pieces were attacked by the fluid just in 

 the same way as if they had not been attached to a voltaic arrangement, 

 provided the vessels did not communicate with each other. 10. The 

 experiment was made as in the preceding case, with the difference only, 

 that the vessels were made to communicate with each other by means of 

 a piece of platium. The positive polar wire quickly underwent oxidation, 

 while the negative one remained untouched. If an aqueous solution of 

 common salt was made use of as the exciting fluid in the pile, and the 

 latter left unclosed, the copper pieces of the voltaic pair rather readily 

 entered into oxidation, while they were not all chemically affected when 

 the pile was closed. 1 1 . A piece either of copper or of iron was connected 

 with each of the poles of a pile ; two tumblers were filled, partly with 

 mercury, partly with water, or with a solution of common salt, and the 



