CHAP, x.] VARIOUS APPLICATIONS OF ELECTRICITY. - 721 



may also be regulated so as to separate the shocks by a greater or 

 less interval. 



The electro-medical apparatus founded on induction are not 

 distinct from each other in their effects ; but they may be classed 

 as M. le Eoux 1 has classed them in two categories, according to 

 the nature of the primitive force they call into action. In the 

 first we have those apparatus in which mechanical force is used 

 to produce an induced current which is made to act again by in- 

 duction on its own circuit, or on a neighbouring one. These 

 apparatus are founded on the relative motion of a circuit and a 

 magnet, and are called magneto-electric. Those apparatus in which 

 an electro-chemical agency is employed to produce the current which 



FIG. 466. Ruhmkorff's electro-medical induction apparatus. 



induces in its own circuit or another neighbouring one, form the 

 second class which M. le Eoux calls rheo-electric machines. Pixi's 

 and Clarke's machines, described in the Forces of Nature, belong to 

 the first class, and Buhmkorff s coil to the second. In Fig. 466 we 

 have a portable apparatus of the latter kind, due to the same 

 inventor, which is principally used in the better class of practice. 



The generating battery for the electricity is formed of two sulphate 

 of mercury elements, seen on the right of the figure. The current is 

 thrown into a double bobbin, and thence passes by the rheophores to 

 two armatures, which the experimenter takes in his two hands. The. 

 interruptions of the current are produced by Neef s contact-breaker 



1 De V Induction et des Appareils Electro- Mcdicaux. 



o A 



