356 DR. MEYER WILDERMAN ON THE CHEMICAL STATICS AND DYNAMICS OF 
pp. 390-391, give the investigation of the different problems, connected with constant 
cells, reversible in respect of the cation, carried out on the system Ag in light, AgN0 3 
solution, Ag in the dark. Each of the plates contains a series of curves. All of them 
have exactly the same course, showing that the curves are characteristic of this type 
of cell. The part of the curves a-b, representing a straight line, gives the position 
of the spot of light from the galvanometer Nalder Nl, when both Ag plates are in the 
dark in a closed circuit (the E.M.F. in the dark having reached in the different plates 
constant and very small values); the part of curve b-c is of a logarithmic shape and 
gives the gradually increasing deflection of the galvanometer, when one of the Ag 
plates is exposed to light (at b) ; the part of the curve c-d is again a straight line, 
and gives the maximum deflection of the galvanometer ultimately reached in light; 
the straight line c-d is running parallel to line a-b, indicating that the system 
(Ag plate in light, AgN0 3 solution in light, AgN0 3 solution in the dark, Ag plate in 
the dark) acquires after a time (after the period given by b-c ) a constant new state in 
light, given by c-d as characteristic of it, as is its constant state in the dark, given 
by ; the further part of the curve d-e gives the gradual diminution of the 
deflection of the galvanometer, when light is removed from the system (at d), i.e., the 
gradual drop of the E.M.F. of the system, when the system gradually passes in the 
dark from its constant state in light to its constant state in the dark. When this 
return is complete, we must evidently get again a straight line, a continuation of a-b ; 
before then it only gradually approximates to its constant state in the dark. 
We note that the system passes in light from the state a-b to the state c-d only 
gradually (not suddenly) and so also on removal of the light the system passes in the 
dark from the state c-d to the state a-b only gradually (not suddenly). It follows from 
this that b-c and d-e represent truly gradual transformations in the state of the 
system, passing from one constant state in the dark to another constant state in light 
and vice versd. We shall call b-c the induction period, d-e the deduction period, 
since the phenomena here are similar to the phenomena of “induction” and 
“ deduction,” observed for chemical reactions (such as CO and Cl 2 ) in light and dealt 
with in the author’s papers on “ Chemical Statics and Dynamics in Light,” ‘ Phil. 
Trans. Royal Society,’ 1903, ‘ Zeit. Physik. Chemie,’ June, December, 1902, &c., &c. 
We notice the course of the induction and deduction periods; b-c, as well as d-e, 
change their curvature, have a point of inflection, changing sign from positive to 
negative or vice versd, and the curves approximate asymptotically either to c-d or a-b. 
Their equations, meaning and content are given in the “ Preliminary Communication 
of Galvanic Cells produced by Light,” ‘Roy. Soc. Proc.,’ Nov., 1904, and will be 
specially dealt with later on. 
Plate of June 3 and 4, 1903 (16 Curves), N2, Table I. 
The Ag plates, prepared as described in § 4, and polished before by the current, 
were immersed in a 0‘25 normal AgN0 3 solution. To know the direction of the 
