1888.] 



the Thermo-electric Properties of Bodies. 

 Fig. 3. 



223 



them in contact. On heating either rod and joining them as before, 

 a current was produced from hydrogen to oxygen across the hot 

 junction. 



The same effect was obtained by decomposing hydrochloric acid 

 solution, in which case we get chlorine instead of oxygen, and the 

 current flows from hydrogen and chlorine. 



If the rod be saturated with S0 2 it is found to act like those 

 containing oxygen or chlorine. 



Resistance. — In the first experiments made to try if any change of 

 resistance took place when wires are saturated with gas, a platinum 

 wire about a yard in length was formed into a spiral, and each end 

 soldered to an insulated copper wire. The junctions were covered 

 with wax, and the wires, carefully insulated with wax, passed through 

 two holes in a cork into a bottle containing dilute sulphuric acid. 

 Through the same cork there passed a thermometer and two glass 

 tubes. The whole was placed in a large vessel of water. After 

 having saturated the wire with hydrogen, the acid was drawn off, 

 and air drawn through for some time. The resistance was found to 

 increase slightly on testing. 



To get rid of possible error from change of temperature, two wires 

 of equal length and section were used and balanced against each 

 other (see fig. 4). 



Fig. 4. 



These were placed in water, and a current passed from the one to 

 the other, allowed to remain in the acid a little to cool if necessary, 

 and afterwards removed, dried, and placed in an empty glass vessel 

 surrounded with a considerable quantity of water. There they rested 

 until the temperature became the same as the water. When measured 



