306 Analyses of Boohs. [April 



platinum plates. Five pairs of zinc and platinum, with two inter- 

 posed platinum plates, yielded a feeble current. Six voltaic plates, 

 and four intervening platinum plates, induced a feeble current. 

 The effects of retardation were altered when variety was made in the 

 nature of the liquid employed between the plates, nitric acid appear- 

 ing to increase the intensity of the current, muriatic acid transmitting 

 a current more easily than pure sulphuric . acid. Increasing the 

 strength of the sulphuric acid caused no change in the effect. 



On varying the nature of the interposed plate, it was found that 

 with one voltaic pair and one interposed zinc plate, as powerful a 

 current was induced as if the interposed zinc plates was absent. 

 With two amalgamated zinc plates there was still a powerful current, 

 but some obstruction occurred. On using three intermediate zinc 

 plates, there was still further retardation, though a good current of 

 electricity passed. Plates of copper seemed at first to occasion no 

 obstruction, but after a few minutes the current almost entirely 

 ceased. 



All these retarding effects exhibit most distinctly the chemical 

 relations and source of the current, and add to the evidence of the 

 identity of the two. 



V. Remarks on the Voltaic Battery. — The action of the battery 

 is weakened by the formation during its activity of substances which 

 may even tend to produce a counter current. In an experiment made 

 by Faraday, the retardation of the current was obviously referable 

 to the state of the film of fluid in contact with the zinc plate, the 

 acid of the film being instantly neutralized by the oxide formed. 



A second cause of diminution in the force or the voltaic battery is 

 that extraordinary state of the surfaces of the metals described by 

 Ritter, which causes them to oppose the passing current. 



The author directs, 1st. That weak and exhausted charges should 

 never be used at the same time with strong and fresh ones, in the 

 different cells of a trough, or the different troughs of a battery, 

 because, the plates in the weaker cells retard the progress of the 

 electricity originating in the stronger cells. 2d. The associating of 

 strong and weak pairs of plates should be avoided, as one part is apt 

 to act as an interposing plate. 



3d. Reversing tin plates, either by accident or otherwise, has an 

 injurious effect, by opposing the current in a manner similar to inter- 

 posed plates of platinum. For, in a series of four pairs of zinc and 

 platinum plates, in dilute sulphuric acid, if one pair be reversed it 

 almost neutralizes the power of the whole. Other causes affect the 

 passage of the electrical current, and there is one especially of com- 

 mon occurrence, viz : when the copper is precipitated upon the zinc 

 in the cells. 



Dr. Davy's paper on the Torpedo oculata and diversicolor, 

 termed indiscriminately by the Maltese, Haddayla, contains some 

 experiments on the electricity of these species of animals, which 

 establish the anticipation of Faraday, that by the application of 

 Harris's electrometer to the torpedo, the evolution of heat would be 

 observed. In his experiments detailed in a former volume of the 



