628 Mr. G. Moody Hobbs on the Relation between P.I). 

 Table IX.— Nickel. (Fig. 12.) 



1st Series. 



2nd Series. 



Distance, 

 X. 



Potential, 

 volts. 



Distance, 

 X. 



Potential, 

 volts. 



2 



2-5 



8 



37 



4 



4-2 



4-5 



5 



6 



170 

 220 

 250 

 350 

 335 

 350 

 330 

 350 

 350 



15 



2 



32 



4 



4-2 



5 



180 

 210 

 280 

 350 

 350 

 350 



(2) Discharges at less than the Minimum Spark-Potentials 

 carried by Metal Ions. — If the discharges corresponding to the 

 above curves from the elbow down are carried by the metal 

 ions, it is to be expected that the nature of the electrode 

 would have an effect upon the position of the elbow, for the 

 force which holds the ions within the metals may be assumed 

 to depend upon the nature of the metal. It will be seen that 

 the above curves completely corroborate this inference. The 

 potential begins to fall below the minimum value at the 

 following distances : — 



Aluminium 5*6 waves. 



Brass 5 



Bismuth 4*5 



Magnesium 4*5 



Zinc 4-5 



Nickel 4-2 



Silver 38 



Antimony 3*5 



Platinum 3 



To illustrate this point the curves previously given are all 

 collected in fig. 13 (PL XIII.). It will be observed that in all 

 these cases the curves have been checked by two sets of ob- 

 servations taken at widely different times. With platinum, 

 brass, and nickel, the observations are very definite and the 

 points lie extremely close to the line, For these metals, 

 therefore, the results are thoroughly trustworthy. In the 

 case of the other metals the results are less definite, as the 



