during the Absorption of Electrons by Platinum. 197 



The value of this definite integral can readily he obtained 

 graphically if* V/(V) is plotted as a function of V. An 

 example exhibiting the method of applying this correction 

 for the difference of potential at different points of the wire 

 will now be given. 



The only set of observations which has been examined in 

 this way are those obtained with the platinum grid saturated 

 with hydrogen No. 7. In this case the observations for the 

 current-E.M.F. are shown thus O in the diagram fig. 5, 

 PL III. The best curve possible was drawn through the 

 observational points and the values of the tangents of the 

 angles of inclination, of the tangents to the various points of 

 this curve, with the axis of voltage were measured. The 

 direction of the tangents was determined by placing a mirror 

 at various points on the curve in such a direction that the 

 curve and its reflexion are continuous. The edge of the 

 mirror is then perpendicular to the direction of the tangent. 

 The tangents were measured at points a distance apart equal 

 to the fall of potential (3*267 volts) along the strip as re- 

 quired by the foregoing theory. From these the values of 



-ntt,^ '/TV) were determined. The values of this function 



were then multiplied by V, the voltage at the negative end 

 of the strip, and plotted on the diagram. The values of 



^ T ,^ V/'( V) are shown thus <g> . Thev are seen to lie on 



a smooth curve passing through the origin. The values of 



w^Sj f(V)dV 



were next found by counting up the number of squares in a 

 portion of the diagram similar to that shaded and bounded 



on the top by the graph of v V/vT), on the bottom by 



the axis of voltage and on the sides by the two vertical lines 

 a distance ^V apart, where "dV denotes the potential drop 

 along the filament. The values of these integrals were then 

 divided by the values of the current i from the strip at the 

 corresponding voltages. The resulting quantities are denoted 

 thus ®. They are seen to lie on a curve, the major part of 

 which consists of a straight line pointing to a voltage equal 

 to 1/2 of the drop of the potential along the filament. Since 

 the diagram represents the voltage applied to the negative 

 end of the filament, it follows that this line points, a> it 



