( 500 ) 
off at f. During this operation care was taken that the interior 
of the vessel remained perfectly dry. The opening g was closed with 
sealing wax. The wire was then annealed by keeping it for several 
hours at 100° C. 
The amylene or the isopentane were distilled into it through the 
side-tube d by means of a flask connected to it by a ground joint. 
After the distillation a tube with phosphorus pentoxide was connected 
to the joint, lest moist air should come into contact with the liquid 
with time and should be absorbed by it. If this had been neglected 
the liquid after some time no longer insulated sufficiently. The 
smallest quantities of water caused short circuiting in the resistance 
which owing to the magnitude of the latter, soon rendered the 
measurements inaccurate. This secondary circuit revealed itself in the 
variation of the resistance and in the appearance of polarisation current 
on breaking the principal current. The glass vessel was placed in 
ice, planed as described in Communication N°. 27. This was heaped 
up till high above the narrowed part. Heaping the ice still higher 
round the neck of the vessel appeared to have no influence. Hence 
we might accept that the resistance came to 0° C. 
When afterwards as leads copper wires of 2 m.m. were used 
it appeared that the operations, required to bring the resistance into 
a zero-vessel, as described above, would, owing to the stiffness of the 
copper wire, prove too dangerous for the cylinder and resistance. 
Therefore (c. f. fig. 2a, Pl. III, Communication N° 27) a tube was 
taken (see fig. 4), closed nearly hermetically at the upper end 
by an india rubber stopper, through which passed the 4 leads ts,..., 4, 
a tube to distil the liquid into it g, a sensitive thermometer (from 
a BECKMANN apparatus), and a stirring apparatus r. 
The thermometer and the stirring apparatus were introduced because 
now the ice cannot be heaped up above the india rubber stopper: 
for fear 1st of introducing moisture, 2nd of conduction between the 
leads through the ice. Then we cannot be certain that the liquid 
takes the temperature of the ice, the more so as the leads are so 
much thicker than in the case considered above. However, when 
the vessel was brought into ice the temperature appeared to differ 
not more than 0.02 deg. C. from 0° C. 
Again a tube with phosphorus pentoxide was connected to the 
joint h, as long as the resistance was kept in the vessel. 
