102 Messrs. Wright and Thompson on the Determination of 
which I pointed out in 1880 is in any fair sense a refutation 
of my theory.  [resnel’s theory of reflection cannot be 
fairly said to be refuted because it leaves unexplained the 
gradual change of phase of the components near the polarizing 
angle. All that is required in order to make my theory 
more complete is a little fearlessness as to complicated 
mathematics, which I regret to say either my laziness or 
my busyness prevents me from displaying, as it has till now 
prevented my noticing Prof. Kundt’s paper. 
I have roughly compared my formula with Prof. Kundt’s 
results, and find that the calculated rotations are of the same 
order of magnitude as he has observed. As he does not give 
experiments on the rotations produced by refiection and 
transmission under exactly similar conditions, any comparison 
must of necessity be rough. 
Yours obediently, 
GEORGE Francis FITZGERALD. 
XIV. On the Determination of Chemical Affinity in terms of 
Electromotive Force.-—Part 1X. By C. R. ALDER Waricat, 
D.Sc. (Lond.), P.BS., Lecturer on Chemistry and Physics, 
and C. Toomeson, F.C.S., Demonstrator of Chemistry, in 
St. Mary’s Hospital Medical School. 
[Continued from p..29.] 
B. Voltaic and Thermovoltaic Constants of Metals immersed 
in Solutions of their Chlorides. 
I. Cadmium. 
180. A number of cells were set up with amalgamated-zine 
and electro-cadmium plates, and solutions of equal molecular 
strength, m MCI, 100 H,0, on each side, and examined pre- 
cisely as before. The following average values were obtained, 
the probable error in each case being from + ‘001 to + -002 
volt. The values of Eq annexed are calculated from the 
heat-valuations of Julius Thomsen, viz. Zn, Cl, aq. =112840, 
and Cd, Cl, aq. = 96250, for molecular strength ‘25 MCI, 
100 H,O ; so that the heat of displacement of cadmium by zine 
from chloride solution m CdCl, 100 H,O is 
112840 —hy —(96250 —h,) = 16590 —(h, —A,), 
where /, and /, are the heats of dilution of zinc- and cadmium- 
chloride solutions respectively from the strength m MCl, 
100 H,O to :25 MCI, 100 H,O: the values of h, and hy are 
derived from the table given in § 160, Part VIII. 
