164 DOVE ON THE ELECTRICITY OF INDUCTION. 



suspended by the use of two springs y y in the shape of a Y, 

 which with their two arms compass both cyHnders at the same 

 time, the one touching wood whilst the other touches metal, and 

 thus upon the principle of the commutator transform alternating 

 currents into currents of a like direction. The points of contact 

 of the one spring are situated diametrically opposite to those of 

 the other, the one y passing from the higher support 10), slides 

 upon the lower surface of both cylinders, the other y passing from 

 2) slides upon the upper surface. This arrangement, applied 

 for the purposes of chemical decomposition, eliminates the gases 

 separately, and moreover in double the quantity they are pro- 

 duced by the usual arrangement, in which the opposing cur- 

 rent is not reversed, but is suspended by interrupting the con- 

 nexion. 



The different combinations of the springs are accordingly the 

 following : — In common experiments without the insertion of a 

 spiral for the production of the extra current, 9) and 3) slide 

 upon the cylinder w,^, as is depicted in fig. 7 ; upon the cylinder 

 Wj, however, instead of the spring proceeding from 5), one that 

 proceeds from the clamp 1), and moreover 1) and 9) conti- 

 nuously, 3) on the contrary intermittently. Alternating cur- 

 rents are however obtained when that which has hitherto been a 

 secondary connexion becomes a chief connexion ; currents iu a 

 like direction, when it is inclined obliquely, and slides on the 

 once interrupted edge. The galvanometer, the apparatus for 

 producing incandescence in platinum and charcoal, as also the 

 human body, are inserted between 4) and 8). For uninter- 

 rupted currents in the same direction, y y alone are used. The 

 arrangement with an inserted spiral for alternating currents 

 is represented at fig. 7- When the sparks of the secondary 

 current are not to be examined, the springs 13) and 14) are left 

 out. With currents of a like direction, the springs y y are in- 

 serted alone in the clamps, whilst the apparatus for measuring 

 the currents is inserted between T and III instead of between I 

 and II. If the current is to be interrupted often during one re- 

 volution of the keeper, the spring 3) is made to slide upon the 

 cylinder w^. 



The weight of the covered wire is 1220 grammes, the thick- 

 ness of the uncovered wire is about i'", its length 880'. The 

 height of the cylindrical rolls of wire is 1^ inch, their diameter 

 14'", that of the outer coil 2A". The front iron plate of the 



