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TENTH ANNUAL REPORT OF 



one, because in this combination the electro-motive force of all tlie 

 polarized pairs of plates is added together. 



For this purpose, the plates 1 and 8 must he placed in conducting 

 connexion with the voltameter, while 2 and 3, 4 and 5, 6 and 7, must 

 be joined by metallic wires. 



PoG:gendorfF has invented an apparatus, called the pole-changer, for 

 effecting these changes and discharges in rapid succession. But his 

 instrument requires the use of mercury, and I propose for the pm- 

 pose the apparatus represented in Fig. 35. 



On a vertical board to the left of the figure is a series of brass 

 pillars, which serve for fastening metal wires. The screw which 

 is used for this purpose is represented only in the one at li ; all the 

 other posts are also provided with screws. These pillars all stand on 

 metallic springs, rubbing against a movable cylinder ; the first and 

 last pillars stand a little below the level of the others. 



At each end of the cylinder a copper ring is placed. The spring of 

 the first ])ost (the wire from whicli passes towards P) rubs on the first 

 copper ring, and the spring of the last post (whose wire goes to Z) 

 rubs on the further ring. 



These wires pass to the platinum and the zinc plates of the charging 

 element. The wires and H, leading to the platinum plates of the 

 voltameter, arc screwed to the first and last of the more elevated 

 pillars. 



The wires 1, 2, 3, 4, 5, 6, 1, 8, which are screwed in the other posts, 

 pass to the platinum plates of the secondary battery. 



