EFFECT OF TEMPERATURE ON CONDUCTIVITY 499 



the employment of an electrical arrangement to bring about 

 the graduated and continuous rise of temperature. 



A certain length of the vegetable nerve on the right arm 

 of the Conductivity Balance was thus raised continuously in 

 temperature, and its conductivity compared with that of the 

 left arm of the balance, the latter being maintained at the 

 temperature of the room, which happened at the time to be 

 33 C. The device by means of which this was accomplished 



FIG. 307. Photographic Record showing Effect of Cooling on Con- 

 ductivity of Plant-nerve 



Balance was obtained at starting, when temperature of both arms was 

 30 C. On cold being applied on right arm, the balance was dis- 

 turbed, showing diminished conductivity on that side. On restoration 

 of normal temperature, the balance is seen at the end of the record to 

 be again restored. 



will be understood from fig. 308. A piece of cork has a 

 small chamber cut into it measuring I cm. each way. In 

 this is placed moist blotting-paper, which keeps it damp, and 

 across it passes a length of I cm. of the right arm of the 

 vegetable nerve in the Conductivity Balance. This cork- 

 chamber has inlet and outlet tubes t and Y. The first of 

 these contains a spiral, H, of platinum, which can be heated 

 to a suitable degree by means of an electrical current, the 



K K 2 



