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leads, for which auxiliary capacities were required. These were 
made on the same principle as the experimental condenser ; metal 
plates which are connected by glass tubes and separated by small 
glass rings. The so formed condenser is then insulated by a layer of 
paraffin and placed in a card-board box coated with tin foil. The 
foil is put to earth so that the capacity is quite invariable and inde- 
pendent of the presence of neighbouring bodies: 
Such an auxiliary condenser is also useful when experimenting 
on a substance with a large dielectric-coefficient, for then the glass 
plate of Nernst’s adjustable condenser may not be sufficiently long 
to give the required change of capacity. In such a case the auxil- 
iary capacity should be put in parallel with the adjustable condenser. 
3. Arrangement of the apparatus. 
In order to avoid the errors arising from the change of capacity 
of the leads, the whole apparatus must be immovably and perma- 
nently fixed. For the same reason the condensers should be very 
carefully switched on and off. This requires the use of a switch 
board to which the taunt wires are fixed and the capacity of which 
is as small as possible. Indeed for this purpose I employed small 
ebonite plates provided with mereury cups which could he connected 
by small metal bars. A diagramatic representation of the arrange- 
ment is shown in Fig. 3. 
+ 
Fig. 3. 
From the two quadrant pairs of the electrometer two wires pro- 
ceed to the mercury cups a and b, and then to the small key 4, 
by which a metallic connection between the quadrants can be made 
and the zero reproduced. From the six other mercury cups ¢, d, ¢ fs 9 h, 
leads go to the inner plates of six condensers Nj, No, 4, B, C, D, of 
which Ni, Ny, are adjustable NERNST condensers and A, B,C. D are 
auxiliary condensers as described above. The outer plates of these 
hd and 
