THE ELECTEIC CONDUCTIVITY OF NITRIC ACID. 



381 



mounted upon a block of ebonite, and provided with a small spring to avoid 

 accidental displacement ; their rotation was prevented by a small arm, A, working in 

 glass tube guides, y. A cord passing over the pulleys, P, P! and P.,, was attached to 

 the upper end of the graduated tube, and the other end to an arm ; this cord could 



Fig. 4. 



be shortened by suitable loops, and the final adjustments effected by means of the 

 kymograph screw, K. The divisions of the tube were observed by a telescope 

 mounted on a rigid stand. 



To secure perfect insulation the cell rested upon and against blocks of ebonite, a, b 

 and c, the two latter being V grooves, against which it was kept pressed by elastic 

 bands. Preliminary experiments already described showed that all fastenings of a 



