Kohlrausch on theElectroscopic Properties of the Voltaic Circuit. 327 



observation first indicated is that pursued in the following expe- 

 riments, the point a being deprived of all electric tension by its 

 direct union with the earth. 



Experiment 1.— The poles of the element were connected by a 

 long fine wire, which was carried in a zigzag manner from side 

 to side of a light wooden frame, and fastened to the latter by 

 pins j the legs of the Vs thus formed were all of the same length. 



a.' Any point (a) being properly connected with the earth, 

 when another point on that side of a from which the positive 

 cm-rent proceeded was connected with the upper plate, the latter 

 exhibited positive electricity; when, however, the point lay at 

 the other side of a, a negative charge was obtained. 



b. As long as the same length of wire existed between the 

 point a and the point examined, exactly the same tension was 

 shown by the electrometer, it mattered not in what portion of the 

 circuit the examination took place. 



c. When a series of points in the circuit at increasing distances 

 from a were examined, the tension was observed to increase, the 

 increase being exactly proportional to the length of wire inter- 

 vening between a and the respective points. Calling to mind 

 what has been said regarding the electric " fall," the case before 

 us shows that, in a wire of uniform thickness, the " fall " is m 

 all places the same. 



Experiment 2. — The poles were united by two silver wires of 

 equal lengths but of different diameters ; the wires being smelted 

 together in the flame of a spirit-lamp, so as to form one unbroken 

 length : it was found, — 



a. That in each of the wires the same electric fall existed 

 throughout. 



b. When one end of the thin wire was properly connected with 

 the earth and the other end proved, the electrometer showed a 

 charge of the strength E ; when one end of the thick wire was 

 connected with the earth and the other end examined, a charge 

 e was obtained j the ratio of E : e was the same as that of the 

 cross section of the thick wire to that of the thin. 



Experiment 3.— The wire connecting the poles was formed 

 of two wires, one of copper, the other of German silver ; the 

 former presenting very little resistance to the current, while the 

 resistance of the latter was considerable. The total resistance of 

 each wire was previously ascertained by means of a rheochord. 

 It was found that the entire increase of tension from one end to 

 the other of the copper wire was to the entire increase along the 

 German-silver wire m the direct proportion of the resistances. 



The above results may be summed up as follows : — In wires of 

 different materials a,,d "of unequal thicknesses, the electric fall is 

 directly proportional to the specific resistances of the metals, and 



