(215) 
conditions were fulfilled in the manner clearly shown in Plate I, which 
represents three different sections of the condenser together with 
the beaker of the cryostat, made to receive the liquefied gas, in 
which it is placed. 
The two outer plates p; and py are connected by the nut s to one 
another and by the pin ¢ with the earth. The three screws s are 
placed in suitable glass tubes on which the five plate condenser is 
itself mounted. The plates themselves have a radius of 3 em. and 
are separated from one another by small glass rods 1 mm. long. 
To reduce the errors so introduced to a minimum these glass rods 
must be made as small as possible, and it appeared to be best to 
cut them from a 1 mm. glass tube with a wall of '/; mm. and 
then to grind them exactly equal. The above mentioned error cannot 
finally be more than 0.1 °/5 since it enters equally into the 
numerator and denominator of the expression for the dielectric 
coefficient. The 1st, 3"d and 5 plates are connected with a pole of 
the induction coil, the 2rd and 4 with the electrometer. The 
necessary wires for this, d; and ds, are fastened to the 1st and 2nd 
plates respectively; they are drawn through small openings in the 
superimposed plates, and continue above through the glass tube g. 
By means of a pin ¢ the whole condenser is fastened to the cover 
of a hollow cylinder of brass m in which the liquid to be investigated 
is placed. The hollow cylinder is earthed together with the two 
outer plates *). 
The method of filling the condenser with liquid gases must now 
be discussed, but some points should be first considered. The condenser 
and hollow. cylinder must be protected as much as possible from 
external heat to prevent the formation of bubbles of vapour, whence 
they are immersed in the beaker B, under the liquid gas. The liquid 
gas must be employed in sufficient quantity to cool the condenser 
and to keep it cold, it must be kept from the deteriorating action 
of atmospheric air, and finally care must be taken that the vapours 
drawn off are not lost. All these conditions can be best obtained 
by the aid of a cryostat i.e. a boiling glass with its cases, such as is 
used in the cryogenic laboratory for measurements with liquid gases. 
The description of the latter can be found in another place 3). 
The following must also be considered. The principle of the method 
1) The section is taken partly through the tube g and partly through the tube NV. 
*) By the wire g. See Plate I, Comm. NO, 51. 
3) KAMERLINGH ONNEs, Comm. NO. 51 § 3. 
