A closely-fitting adjustable piston is provided at one end.
II, S is kept permanently closed, and corresponding values of H and B are determined by one of the two methods already described, the strength of the battery-current being varied by means of the adjustable resistance R.
AB is the axis of rotation, BC an adjustable FIG.
The beam must be provided with a small ball of metal which can be screwed up and down a stem on the top of the beam for the purpose of accurately adjusting the position of the centre of gravity, and there should be a small adjustable weight on a fine screw projecting horizontally from one end of the beam for the purpose of accurately balancing the arms.
23, representing the " differential " method, B is the sending battery, B 1 a resistance equal to that of the battery, R a rheostat and C an adjustable condenser.