Prof. E. Wai'tmann'sj^?^rM Memoir on Induction. 247 



nation in the closing of the two circuits, only either the direct 

 or the inverted currents are received. This double effect may 

 be obtained by changing the point of contact with one of the 

 springs, or by varying the position of one of the wheels on the 

 axis relatively to the other. Two wheels do not permit of 

 giving the same direction to the direct and the inverted cur- 

 rents ; because as it is evident that the induced circuit must 

 communicate with the two wheels when the principal current 

 is closed, a part of this current may proceed from the wire of 

 induction and modify the effect of the direct induced current. 



127. Lastly, if it be desired to isolate only the inverted in- 

 duced currents, the rheotrope may be reduced to a single 

 wheel. It is sufficient for the proposed object to open the 

 induced circuit when the inducting circuit is closed, and vice 

 versa. But this arranijement would not be suited to isolate 

 the dn-ect induced currents, because it would be necessarj' to 

 close simultaneously the two circuits, and the voltaic current 

 would be propagated in the double channel presented to it. 



128. It will be found convenient to mark letters on the dif- 

 ferent pieces ^, h\ i', r', s', t\ and to repeat them at the extre- 

 mities of the metallic conductors employed to connect these 

 pieces. These conductors will be fixed to the interior of the 

 lid of the case which contains the whole electro-electric ma- 

 chine; and a brief direction will indicate which ought to be 

 employed to produce the effects corresponding to the differ- 

 ent possible cases. 



129. It is understood that the commutator with three or 

 with two wheels is applicable to all magneto-electric machines, 

 telegraphs, clocks, &,c., whose motive principle is the electri- 

 city of the magnet or of the battery. 



§ XV. Employment of induced currents to restore sensation. 



ISO. The cases of nervous weakness which have yielded to 

 a judicious application of electro-physiological shocks and 

 discharges are too well ascertained to admit of any question. 

 Since the marvellous effects of aether have been known, I have 

 proposed to several physicians the employment of the electro- 

 electric machine, or at least of intermittent currents of very 

 short duration, to obviate the dangers which the injection of 

 too strong a dose of this liquid, or a too prolonged inhalement 

 of it, might produce. I have made some experiments* with 

 a view to verify the accuracy of my expectations; and although 

 they are so few as to require to be repeated and varied, I shall 



* In company with Dr. A. P. Prevost, and Mr. Schnetzler. I take this 

 opportunity of thanking these gentlemen for their zealous cooperation. 



