82 



WRITINGS OP JOSEPH HENRY. 



[1835 



Fig. 3. 



a broad stem on the bottom ; one soldered 

 to the zinc plate, and the other to the cop- 

 per case. The cavity in these cups is 

 about three eighths of an inch wide, a 

 little more than an inch long, and half 

 an inch deep. The cups being well 

 amalgamated and partially filled with 

 mercury, receive the ends of the copper 

 conductors which unite the several ele- 

 ments. 



For the purpose of suspension, a slip of copper, b b, with a 

 hole in it, is soldered to each upper corner of the copper 

 case; these fit loosely into a mortice or narrow groove in the 

 cross pieceSj and are secured by a pin of copper wire. When 

 the pins are withdrawn, a single element may be removed 

 from any part of the series, without disturbing the re- 

 mainder. 



The zinc plate is fastened into its copper case, without 

 touching, by a piece of wood at each corner with a groove 

 in it to receive the edge of the plate. The grooves in the 

 two lower pieces of wood terminate at about a quarter of an 

 inch from the lower end, and thus form shoulders, which 

 prevent the plate from slipping down ; while the wood itself 

 is supported by a flange, formed by bending in the lower 

 edges of the corner of the case. ' 



There are two principal sets of connectors; the first is 

 formed of bars of cast copper thirteen inches long, an inch 

 wide, and about an eighth of an inch thick. On the lower 

 side of these are eleven broad projections, which fit loosely 



Fig. 4. — Homogeneous Connector. 



into a row of cups on the plates of zinc or copper. Fig. 4 

 represents one of these connectors with a thimble soldered 

 on the upper side for the purpose of attaching a conductor, 

 which may serve as a pole. 



