428 
LORD RAYLEIGH AND MRS. H. SXDGWICK ON THE 
a horizontal position near the top of the solution. In order to protect the kathode 
from disintegrated silver, which in our experience is invariably formed upon the anode, 
the latter is wrapped round with pure filter paper, secured at the back with a little 
sealing-wax. This arrangement appears to us for several reasons preferable to the 
vertical suspension of the electrodes in the form of flat plates. In the latter arrange¬ 
ment the deposited metal usually aggregates itself upon the edges and corners of the 
kathode with a tendency to looseness. Again the solution rapidly loses its uniformity. 
At the kathode the solution becomes impoverished and at the anode it becomes 
concentrated. With vertical plates the strong solution soon collects itself at the 
bottom, and the weak solution at the top, so as to give rise to considerable variation 
of density. It is true that the horizontal position of the electrodes necessitates the 
use of a porous wrapping, which would increase the difficulty of determining the loss 
of weight at the anode. M. Mascart appears to have succeeded in determining this loss, 
but the disintegration which we have always met with rendered the attempt on our 
parts hopeless. It is possible that something may depend upon the mechanical con¬ 
dition of the metal, but as to this we cannot speak with confidence. The blackish 
powder left upon the anode has at first the appearance of being due to chemical 
impurity, but it occurs with anodes of the highest quality of silver, and is completely 
soluble in nitric acid. 
In our earlier trials, dating from October, 1882, we were much impressed with the 
importance of obtaining sufficient coherence in the deposit to guard against risk of 
loss in the washing and subsequent manipulations. The addition of a very small 
proportion of acetate of silver was found to be in this respect a great improvement, 
affording a deposit less crystalline in appearance and of much closer texture ; and in 
consequence nearly all our experiments during the first year were conducted with 
solutions containing sensible quantities of acetate. In order to detect whether 
anything depended upon the “ density ” of the current, two platinum basins of 
different sizes were employed, the area of deposit being in about the proportion 
of 2 : 1, but no distinct systematic difference was observed. When the deposits were 
completed the basins were rinsed several times with distilled water, and then allowed 
to soak over night. The next day after more rinsings they were dried in a hot ah' 
closet at about 160° 0, and after standing over another night in a desiccator were 
carefully weighed. Repetition of these weighings after intervals of standing in the 
desiccators showed that they were correct to milligrm., so that as the total weights 
of deposit amounted to 2 or 3 gratis., a high degree of accuracy in the final evaluation 
of the ratio of deposit to current was expected. Discrepancies, however, presented 
themselves of an amount much greater than we had been prepared for, and they 
were of such a character as to show that the disturbing causes were to be sought in 
the behaviour of the voltameters and not in the current weighing apparatus. Thus it 
was found that the numbers obtained on the same occasion from the two voltameters 
in series, through which exactly the same quantity of electricity had passed, were 
