LARGE DOUBLE-CURRENT VOLTA-FARADIC APPARATUS. 245 



Fig 52. 



the suppression of the toothed wheel D, fig. 51, which is replaced 

 by a pedal rheotome Y, fig. 52, the mechanism of which will be 

 explained hereafter, and which has rendered it possible to dispense 

 with the numerous connections of the first instrument, and much 

 to simplify the construction ; 2, by a graduation, acting by means 

 of a tube of copper, B, which covers more or less of the two coils 

 which afford the double induction ; 3, by the use of a tube, F, 

 containing water, and called the moderator, which, in combination 

 with the graduator tubes, renders it possible to measure the smallest 

 doses of electricity, as well as those that are larger; 4, by the use of 

 a commutator of the coils, E (fig. 55), the use of which will be ex- 

 plained ; 5, and last, by a considerable modification of the battery. 

 I proceed to the description of the apparatus as modified by 

 these changes, and with reference to figures 52, 53, 54, 55, and 56, 

 for illustrations of the several parts. 



Fig. 53. 



