Inductive Capacity of Electrolytes. 189 



else both conductivity and inductive capacity were due to 

 some common property of these liquids. In short, that the 

 measured specific inductive capacities of conducting liquids 

 were not genuine specific inductive capacities, the square 

 roots of which, according to the electro-magnetic theory of 

 light, should equal the corresponding indices of refraction, for 

 waves of periods equal to those employed in measuring K. 

 As will appear from the following pages, this anticipation has 

 not been realized, the experiments indicating that these large 

 values are true inductivities. 



II. The method adopted for studying the question was to 

 measure the force exerted between a fixed and a movable 

 electrode in an electrolytic cell, varying the difference of 

 potential of the electrodes, their distance apart, the periods of 

 the alternating potentials employed, the temperature of the 

 electrolyte, and its conductivity (the latter by varying the 

 quantity of dissolved salts or other impurities). Water and 

 alcohol are the electrolytes studied, and their behaviour has 

 been compared with that of air, turpentine, and other di- 

 electrics. 



Apparatus. 



The apparatus containing the electrolytic cell is shown 

 in Plate VI. fig. 1. The movable electrode is suspended 

 by a fine silver wire ('009 centira. in diameter) which 

 conducts the current * to the electrode and whose torsion 

 measures the force of attraction in question. The silver wire is 

 attached above to the torsion-head a, and below at the mirror 

 c to a thick wire which passes down into the liquid (contained 

 in the glass dish d) ; then, bending at right angles, it forms an 

 arm about 4 centim. long, at the end of which is attached 

 the movable electrode, hereafter called the needle. Several 

 forms of needle were used, but in order to secure a quick, 

 nearly dead-beat motion, it was usually constructed of from 

 two to five narrow plates above one another in horizontal 

 planes, held together by vertical wires. The fixed electrode 

 consists of a vertical plate of platinum, 3^ X 5 centim. It is 

 attached to a brass piece which slides in a slot in the ebonite 

 plate e, and a graduated scale s permits the plate to be set at 

 any desired point. All parts dipping into the liquid are made 

 of platinum. A scale at a distance of three metres is seen by 



* The current traversing this wire in the experiments was not sufficient 

 to change its temperature as much as the ordinary fluctuations in the 

 temperature of the room. 



