in Cells for Direct and Alternate Currents. 



339 



that is to say between the terminals of the alternate current machine 

 a small non-inductive resistance and a Siemens dynamometer were 

 the only part of the circuit other than the cells experimented upon. 

 The copper resistance of the circuit including armature was from 1 

 to 5 ohms. 



In the first portion of these experiments, the results of which are 

 given in Table IV, the instantaneous values of the current, and the 



Table IY. 



potential difference between the terminals of the cell, were observed 

 by aid of a Kelvin quadrant electrometer and a revolving contact 

 maker. The cell across which the potentials were observed con- 

 sisted of one aluminium plate T T g- inch thick separated by J inch from 

 a carbon plate J inch thick, the electrolyte being a saturated solution 

 of potash alum in water. The surfaces thus opposed to one another 

 in this electrolyte have each an area of 36 square inches. Another 

 cell of the same size as the above was placed in series with this cell. 

 Four smaller cells were used in some of the experiments as will be 

 set forth. Each of these consists of a thin aluminium plate opposed 

 to a carbon plate, the opposed surfaces in a saturated solution of 

 alum have each 8 square inches area, the distance between such 

 surfaces being J inch. 



In Table IV the arrangement of these cells was as follows : 

 Experiments (1) and (2) all the six cells in series. Experiment (3) 

 the two large cells in series with one another and with the four 

 small cells arranged 2 series 2 parallel. Experiments (4) and (5) 

 only the two large cells in series were used. No attempt was made 

 to cool or circulate the electrolyte, but it had considerable volume 

 and took some time to heat and cool. In all cases there was an 

 excess of salt to insure saturation. Table IV contains the important 

 information obtained from the tests. 



These figures show that small currents are accompanied by large 



