188 



SCIENCE. 



[Vol. I., No. 7. 



the centre one having double the length of the 

 others. The side-pieces communicate hy means 



N°1 , ^[(xchxjn-tz- Ttiri^iiin' 



of auxiliai-y conductors, — that on the left with 

 the contact piece of the terminal E, that on 

 the right with the contact piece of the terminal 

 GC. 



The movable contacts, to the number of 

 eight, are shown in the figure. Thej^ are all 

 carried on one plate, free to move around the 

 centre of the apparatus. The two innermost 

 contacts are. conuected together so as to form 

 a sort of U ; the next pair forms a larger U ; 

 and the four others are connected, two and 

 two, bj' circular strips. The different pairs of 

 contacts are, of course, insulated from each 

 other. A handle in the centre of the movable 

 plate serves to place it in different positions. 



Suppose, for example, that the movable 

 contacts are in the first position shown in the 

 figure for quantity. The terminals 1 and 2 

 being, at the same instant, poles of the same 

 name, the current enters siniultaneouslj' by the 

 two movable contacts corresponding to these 

 terminals, and passes at the same time into the 

 small cable and the cable in which is the electro- 

 magnet. After passing the carbons, it is re- 

 united in one conductor, and returns by the 

 large cable to the terminal G C. On the fixed 

 contact of double size, in connection with this 



terminal, rest the two movable contacts by 

 which the current returns to the terminals 3 



and 4. 



In coupling for ten- 

 sion in the same ma- 

 chine, the current, leav- 

 ing the first circuit of 

 the machine by the ter- 

 minal 1, traverses the 

 most open pair of mova- 

 ble contacts, and ar- 

 rives at one of the low- 

 er fixed contacts by 

 means of the conductor 

 auxiliarj' to the contact 

 G C. It then follows 

 the large cable, passes 

 through the carbons, 

 and only traverses the 

 small cable of the elec- 

 tro-magnet to arrive at 

 the terminal E ; thence, 

 by the second auxiliary 

 conductor, to the small- 

 est pair of movable con- 

 tacts and terminal 4. It 

 then traverses the sec- 

 ond circuit of the ma- 

 chine, and returns to the 

 terminals. Afterwards, 

 by the second pair of 

 movable contacts, it arrives at the large, lower, 

 fixed contact, from which it is conducted bj- the 



2^'.' ^ . Ma^h-it!^. Ji'^iQtfjri' 



I .'ii'MCIolHiaUTEUit DF ;;iJUH,\ 



third pair of movable contacts to the terminal 2 ; 

 that is to say, to the first circuit of the machine. 



