1888.] the Thermo-electric Properties of Bodies. 221 



pressed together, so that one forms a continuation of the other, and 

 the wire on one side of the junction is heated, no current is obtained, 

 but he observed a current in all cases where there was dyssymmetry." 

 When repeating these experiments, I was led to commence a research 

 on the effect of occluded gas by the following curious phenomenon. 

 Two pieces of platinum wire of 0*9 mm. section, and of 925 mm. length, 

 were stretched with weights only just heavy enough to keep them 

 straight. They were placed at right angles to each other, the centres 

 being in contact, and the ends bending down into mercury cups (see 

 fig. 1). Each wire after being carefully annealed was joined up to a 



Fig. 1. 



galvanometer, and the absence of currents from strain proved by 

 heating with a small flame. When both wires were found to be 

 perfectly free, they were brought together in the middle, and one end 

 of each connected with the galvanometer. On heating the wires near 

 the point of contact thermo-electric currents were produced, but after 

 heating the junction of the wires to a bright red for a little time and 

 allowing it to cool, the currents produced by heating the wires on 

 either side were opposite in direction to those produced before. After 

 resting from Saturday until Monday the change in the wires, produced 

 by heating the point of contact, was found to have disappeared, and 

 the currents produced by heating the wires to be the same as at 

 first. 



This naturally suggesting that some kind of temporary change took 

 place in the wire, when heated in a Bunsen lamp, and that this might 

 possibly be produced by the gas absorbed by the platinum at a high 

 temperature, I was induced to commence a series of experiments on 

 the effect of occluded gases on the electrical properties of bodies. 

 A piece of platinum wire about 18 inches long was bent in the 

 middle, and one-half protected by being covered with glass tube and 

 made water-tight at the lower end. After annealing the free portion 

 and testing until perfectly free from all strain effects, it was placed, 



