Torsion of Lead Wire beyond the Elastic Iimit. 551 
Fig. 9 isa diagram of the apparatus. As before, water 
is used as the load, but in this case it is necessary that the 
whole weight on the wire should ultimately be removed. 
Bia g, 
TT 
The vessel B which is suspended from A (the wire under 
test) is therefore placed on one pan of the balance C, and 
weights rather more than the weight of the vessel are placed 
in the other pan. The pull on the wire A at any time is the 
difference between the weight of B and the water it contains 
and the weights on the other pan of the balance. The whole 
of the weight on A can therefore be removed if necessary by 
means of the syphon. 
F is a brass plate (shown on a larger scale in fig. 10), 
suspended at its corners 6 by three lead wires. Its weight is 
10 grams, so that the tension in each wire is 3°3 grams. The 
piece P is not fixed, but can be unscrewed at cc leaving the 
hole Q open. E,a piece of brass soldered to the end of 
the wire under test, passes through the hole Q, and then P 
is placed through O underneath the point a. The point is of 
platinum, and P is a flat piece of brass covered with platinum 
foil. These two form the contacts, and it will be seen that 
the point of contact is on the axis of A (fig. 9). 
As it requires 0°2 ampere to work the electric valve DKL, 
it is necessary to introduce relays R, and R, to reduce the 
current between E and F to ‘002 ampere, so that making and 
