THE ROYAL ARTILLERY INSTITUTION. 
153 
Upon the middle of the base a brass cylinder d is fixed, containing a 
spiral spring e, and piston f- } at one extremity of the piston is an ivory 
buffer g, at the other extremity a brass handle h. When the piston rod is 
drawn back it cocks on a trigger i placed behind in a direction perpendicular 
to the rod. 
When the disjunctor is thus cocked the ivory buffer no longer presses 
against the two straight springs, and the two pair of screws with platinum 
points are allowed to come in contact with each other. Then, if one electric 
circuit includes the two pressure screws on the right, and another electric 
circuit the two pressure screws on the left, free communication will take 
place, as the little platinum pointed screws will be touching. But if the 
button on the trigger be pressed, the piston rod is allowed to fly back, and 
the ivory buffer strikes against both the springs, and by detaching the points 
of the little platinum pointed screws from each other, breaks both circuits 
exactly at the same moment. 
Adjustment of the Apparatus. 
5. The apparatus must be placed in a spot well sheltered from wind and 
dust, and at a sufficient distance from the gun to avoid the disturbing 
influences arising from the shock of the discharge. The pendulum and 
conjunctor are set upon a solid heavy table, perfectly insulated from the 
building in which it is erected. The disjunctor is set on a table placed 
beside the other. 
6. It is important that the pendulum should be so adjusted, that the 
oscillating system, in vibrating from its initial position to that of equilibrium, 
should pass through an arc of 75°. This is performed by means of the two 
levelling screws on the left of the base, and the adjusting screw on the 
right. 
The suspension of the pendulum is regulated, so that the washer is made 
to oscillate as near as possible to the poles of the large electro-magnet 
without touching them. 
7. In the conjunctor care is taken that the mercury is quite pure, and 
the point of the pin free from oxidation. 
In the disjunctor the platinum pointed screws are arranged, so that there 
is an interval between their respective points something greater than the 
thickness of a piece of writing paper. 
Voltaic Batteries. 
8. Two batteries must be employed, the elements may be either those of 
Bunsen or Grove. 
The battery should be outside the room in which the instrument is, but 
should not be removed very far, in order that the current which magnetizes 
the large electro-magnet, may meet with as little resistance as possible. 
