5 76 
MESSRS. R, T. GLAZEBROOK AND S. SKINNER ON THE 
§ 10. Method of Carrying out an Experiment. 
The usual method of conducting the observations was as follows :— 
The platinum bowls were washed with nitric acid and distilled water, dried by 
heating in a gas flame, and left to cool, usually overnight, in a desiccator. They were 
then weighed and placed in position, being tilled with the solution, the anodes were 
immersed and the necessary connections made ; "while this was being done the current 
was allowed to flow in the main circuit through the alternative wire, and the value ot 
the resistances required in the boxes to balance the Clark and the potential difference 
then existing between the ends of the strip coil approximately determined. 
In cases in which the bottle cell No. 90 was used the difference between its E.M.F. 
and that of the standard Rayleigh No. 1 was found by the usual opposition method. 
The main current was then broken and the difference in resistance between the 
strip coil and the standard “Flat” determined by Carey-Foster’s method, the neces¬ 
sary temperatures being observed. 
The main current was then made, still through the alternative wire, and the 
resistances in the boxes required to balance the Clark accurately taken. The plugs 
were then set to the approximate value required to balance the potential difference 
between the ends of the strip coil, and the key in the main circuit shifted so as to 
send the current through the voltameters, the time being noted on the chronometer. 
Some small changes in the resistance boxes or in the mercury rheostat were usually 
required to obtain a balance in the galvanometer circuit. These were made and the 
spot of light watched, as already described, the necessary changes being made from 
time to time to keep it at rest. 
After the experiment had proceeded for some time a comparison between the Clark 
and Leclanches was usually again made as rapidly as possible. This was done by 
shifting the connections from L and M into the cups A and C, the current in the 
main circuit not being interfered with. The connections were again restored to their 
original position and the experiment proceeded as before. After the current had passed 
for some time, usually from forty minutes to an hour, it was again broken, the time 
being noted. 
A comparison between the Clark and the Leclanches was again made, and the 
differences between the electromotive forces of the bottle cell No. 90 and the standard 
and between the resistances of the strip coil and flat were observed. 
The temperatures of the bath containing the strip coil and of the bottle and 
standard cells were noted from time to time during the experiment. 
While the comparisons of E.M.F. and of resistance were in progress the bowls 
were rinsed with distilled water and then left to soak overnight in distilled water. 
The next morning they were again rinsed with distilled water and alcohol and then 
dried in a hot air bath, at a temperature of from 1G0° to 180° C. 
After cooling for some hours in a desiccator the} 7 were weighed. The weighings 
