1889.] Electrolytes to very rapidly alternating Currents. 285 



the coil C are supported in an ebonite frame provided with an 

 ebonite screw, by means of which the two balls can be brought very 

 near together and kept so as long as is necessary. 



The coils B and C are placed on shelves of glass coated with 

 shellac. The shelves are supported on a framework with supports at 

 different levels, as in an ordinary book-case, so as to enable the dis- 

 tance between the primary and secondary coils B and C to be altered 

 if necessary. The coil A is connected to an induction coil which, 

 when in good order, will give sparks 5 or 6 inches long. The coil is 

 worked by a slow mercury break, the speed of which can be regu- 

 lated by altering the inclination of the arms of a fan whose motion 

 resists that of the break : in the actual experiments the circuit was 

 broken every few seconds. When the coil works sparks pass between the 

 points e and /, electrical vibrations are started in the coil B ; in other 

 words, there are alternating currents in B whose period is that of its 

 electrical vibration, and given by equation (18). The currents in B 

 will induce currents in C, and these latter will be rendered evident 

 by the production of a minute spark between the two balls at its 

 extremities. These sparks, though small, are so bright that they can 

 be readily observed without darkening the room. 



The production of sparks in the secondary circuit is much affected 

 by what are, apparently, slight alterations in the conditions of the 

 primary. Thus, for example, it is very much facilitated by placing 

 the balls of a pair of discharging tongs between e and /, and allowing 

 the spark to jump from e to the discharging tongs, and then from the 

 discharging tongs to /. This change did not seem to be due to the 

 resonance between the coils B and C being improved by the presence 

 of the tongs, for unless they were placed in the way of the spark they 

 produced no effect ; again, it was not altogether due to an increase in 

 the quality of electricity which passed from A to B at each discharge, 

 as this was measured by placing a specially insulated galvanometer in 

 the circuit, and it was sometimes found that the quantity of elec- 

 tricity which passed when the tongs were not interposed and when no 

 spark was produced in the secondary circuit, Was greater than the 

 amount which passed when the tongs were interposed and when 

 sparks were produced. The character of the spark which passes 

 between A and B has also great influence the best sparks are those 

 which are perfectly straight, and accompanied by a sharp snap ; zig- 

 zag sparks in the primary very rarely produce any sparks in the 

 secondary. 



A conducting plate placed between B and C ought, as we have seen, 

 to diminish the induction between them, and therefore the electro- 

 motive force in the circuit C, and since the diminution in the induction 

 increases with the rapidity with which the current in the primary is 

 reversed, it ought in this case to be very marked. This was found to be 



