48 ]\lr. H. Medlock on the Reciprocal Action of Metals 



cess as that adopted by Faradiiy with tlie Gi/mnotus. They con- 

 sisted of strips of strong phuinum-foil, 5 niillims. in breadth, 

 bent into the form of tlie transverse section of the fish, and were 

 55 niillims. in length for the thiek anterior part, and 45 millinis. 

 in length for the thinner caudal extremity. To these strips 

 copper wires coated v/ith gntta-percha were soldered, serving as 

 insnlating handles ; the soltlcred parts were carefully covered with 

 varnish. The wires were connected with the ends of a multiplier 

 of 550 convolutions, with heavy double needles. The platinum 

 saddles in Spree water produced no effect upon this multiplier. 

 Lastly, in accordance with Galvani's arrangement for the Tor- 

 pedo'^', a prepared frog was so placed upon the edges of the glass 

 jar, that it could not but betray by its convnisions every dis- 

 charge of the fish. 



When the saddles were placed upon the head and tail of the 

 fish, the frog was convulsed, and the needle flew round the dial 

 in a direction which indicated tke head to be negative and the tail 

 positive, or a current in the organ from the head to the tail, and in 

 the surrounding water and the ivire of the multiplier from the tail 

 to the head. The experiment was repeated again with the same 

 result. I ascertained that the magnetism of the needles had 

 undergone no perceptible alteration. 



M. Bilharz's ])rediction consequently has not proved true. 

 The current in the Malapterurus has a direction opposite to that 

 in the Gijmnotus. If a pile of the organ of the Torpedo, in 

 order to become one of the organ of the Gi/mnotus, must bend 

 forwards with its ui)per end, in order to become a column of the 

 organ of the Malapterurus, it must lean the same end backwards. 



VII. On the Reciprocal Action of Metals and the Constituents of 

 Well- and River-ivaters. By Henry Medlock, Esq.-\ 



II. The Action of Iron, 

 TN a paper published in the September Number of the Pbilo- 

 -1- sophical IMagazine, I pointed out the peculiar action of 

 certain constituents of water upon lead. When nitrogenous 

 organic matter is contained in the water of a stream, a portion of 

 the nitrogen is in time converted into ammonia. Part of this 

 ammonia in the ordinary course of oxidation is converted into 

 nitrous acid, which combines with an equivalent of ammonia and 

 forms nitrite of ammonia. The nitrite thus produced may be, 

 and probably is, converted by time into nitrate of ammonia. 



* Memoriesulla Elettricitu animate., ., al celebre Abate Lazzaro Sual- 

 lanzam, &c. Bologna, 1/97, iv. p. 74. 

 t Communicated by the Autlior. 



I 



