S74i M. Ampere's Memoh- 



columns EF, E'F', are raised, connected with one another by 

 means of two transverse bars LL', FF'; an axis G FI is main- 

 tained between these two bars in a vertical position. Its two 

 extremities G, H, terminating in sharp points, enter into two 

 conical apertures, situated one in the lower transverse bar 

 LL', the other in the end of a screw KZ, borne by the upper 

 transverse bar FF', and destined to press on the axis GH 

 without forcing it. In C is firmly fixed to this axis an arm 

 QCO, of which the extremity O presents a hinge, in the centre 

 of which is engaged an arc of a circle AA' formed by a 

 metal wire which always remains in a horizontal position, and 

 the radius of which is the distance from the point O to the 

 axis. This axis is balanced by a counterpoise Q, for the pur- 

 pose of lessening thefriction of the axis GH in the conical aper- 

 tures in which its extremities are received. 



Above the arc AA' are arranged two small troughs full of 

 mercury, in such a manner that the surface of the mercury 

 rising above the edges shall always come within the arc A A' 

 in B and B'. These two troughs communicate by means of 

 metallic conductors MN M'N' with cups P, P' full of mercury. 

 The cup P and the conductor MN which unites it with the 

 trough M, are fixed to a vertical axis entering into the table 

 so as to be capable of turning freely. The cup P', to which 

 is fixed the conductor M'N', is intersected by the same axis, 

 round which it turns as independently as the other. It is 

 isolated from it by means of a glass tube V which covers this 

 axis, and by a glass shield U which separates it from the 

 conductor of the little trough M, in a mamier that the con- 

 ductors MN, M'N' may be placed at any angle that may be 

 desired. 



Two other conductors IR, I'R' fixed to the table are re- 

 spectively immersed in the cups P5P', and make them com- 

 municate with cavities R,R'' made in the table and filled with 

 mercury. A third cavity S, also filled with mercury, is between 

 the two others. 



The following is the process for using this apparatus : 

 Immerge one of the rheophors (for instance, the positive) into 

 the cavity R, and the negative into the cavity S, which is put 

 in communication with the cavity R' by a curved conductor of 

 any shape. The current will follow the conductor RI, pass 

 into the cup P, thence into the conductor NM, into the trough 

 M, into the portion BB' of the arc AA', in the trough 

 M', the conductor M'N', the cup P', the conductor I'R', and, 

 at last, from the cavity R' into the curved conductor which 

 goes into the cavity S in which the negative rheophor is , 

 pliinged. - , , 



According 



