Mr R. Adie on Electrical Experiments. 301 



inch square, with 2 attached thermometers, was arranged in every 

 way the same as in the experiment with the bismuth bar. The 

 observed temperatures were, room 49° ; positive end 50^° ; negative 

 60.° The same experiment repeated with a 2 pair battery — room 

 45° ; positive end 49° ; negative end 48°. 



The iron conducting wires were changed for lead ones, and the 

 current derived from 1 pair passed through the copper as before ; 

 the observed temperatures were, room 49°; positive end 55° ; nega- 

 tive end 56°, In these experiments, the temperatures of the con- 

 ducting wires and bars must act and re-act on one another through 

 their metallic contact. In the iron wire the resistance to conduction 

 is not sufficient entirely to counteract the natural action of the 

 electricity on the bar of copper ; but with lead conducting wires, 

 where the resistance is increased, the negative end is 1° warmer 

 than the positive ; at the negative end the electrical current has to 

 enter lead, which it heats considerably, on account of its bad con- 

 ducting power, the lead re-acts on the copper, and produces this 

 apparent elevation of temperature at the negative pole of the copper 

 bar, which is due to the electrical current entering into a lead bar, 

 or acting on it as a positive pole. With bismuth conductors, the 

 change would, I apprehend, be still greater. 



In these experiments, electricity passes through matter in its thre^ 

 different conditions of gaseous, fluid, and solid, and in all of them 

 heats the part where it enters higher than the part where it quits the 

 medium. 



38. Figure 2 represents one of M. Pel- ^'e- ^^ 



letier's crosses. BD, a bar of antimony, 

 8 inches long, .2 square ; C E, a similar 

 bar of bismuth fastened together at their 

 centres A, either by soldering, or by 

 cleaning the surfaces of the bars where 

 they are in contact and binding them 

 firmly together by cord ; H B and I C 

 are copper wires soldered to the bars at 

 band C, for the purpose of conveying a 

 current of electricity from a battery ; 

 E F and D G, are similar wires joined 

 for connecting with a galvanometer. 



When a current is circulated through the joint A in the direction 

 B A C, a galvanometer attached to the extremities of the wires F and 

 G is deflected, as if the joint A was heated ; but when the current 

 is circulated in the direction, CAB, the action on the galvanometer 

 is the same as if a piece of ice had been placed on A. This result 

 is constant for all electrical currents, at least within the limits of 

 intensity given by a thermo-battery, and a 10 cell zinc and silver 

 battery. To shew the connection of these currents which act on the 

 galvanometer, with the variations in temperature produced by the 



