G A L V A N I C I N ST HU M E NTS . 



Fig. 337. 



329 



PC c 



between the several sheets and the tin masses is effected. 

 Between the letters z z , the zinc only is in contact with the 

 masses. Between c c the copper alone touches the tin. At 

 the back of the frame, ten sheets of copper between c c, and 

 ten sheets of zinc between z z, are made to communicate by 

 a common mass of tin, extending the whole length of the 

 frame between T T ; but in front, as shown in the larger 

 figure, there is an interstice between the mass of tin connect- 

 ing the ten copper sheets, and that connecting the ten zinc 

 sheets. The screw forceps, ff, may be seen on each side 

 of this interstice, holding the wire which is to undergo igni- 

 tion. A wooden partition, p p, separates the two sets of 

 plates of which the apparatus is seen to be composed. ^The 

 swivel at S permits the frame to be swung round after 

 being taken out of the acid in A, and to be lowered into the 

 pure water in a ; this is for the purpose of washing off, after 

 an experiment, the acid which might otherwise too rapidly 

 corrode the plates. 



Dr. Hare, the inventor, regards this as furnishing an ex- 

 treme case of great heating power with low electric intensity, 

 and also as showing that the quantity of heat evolved in 

 28* 



