15 
At p on the chart there is a small scale q, of which the free extremity slides 
upon the conducting arc o. 
Near the gun itself, at P, there is another arc 0, and scale Q, solidly attached 
to the gun. 0 and o are connected by the Bridge, 5 6 7 8, so that the galvano¬ 
meter G is at zero when Q is parallel to q. Therefore when the position of the 
object has been marked on the chart the scale q is passed through the point indi¬ 
cated, and the gun, with Q attached to it, is traversed until the galvanometer G 
marks zero. The gun is then pointing at the object. The angle of elevation 
may be telephoned to the gun, or else transmitted electrically by means of the 
quadrants R and r, the Bridge 9 10 11 12, and the galvanometer G'. The same 
observatories and the same central post may serve several batteries. It will only 
be necessary to indicate their positions on the chart, and have a scale for each. 
Pig. 15 represents the arrangement of a gun with the above apparatus. The scale 
Q, is firmly fixed to the centre of the gun carriage, and is therefore in the same 
vertical plane as the axis of the piece. The quadrant R is fixed to a bracket of the 
gun carriage, and its index to a trunnion. Elevation or depression is then given 
until the galvanometers G and G' are both at zero. 
Fig. 15. 
VI. Telescope for Laying Ship Guns. 
This invention of Captain Fiske’s has no scientific connection with the preced¬ 
ing ones. It is represented in the figures 16 and 17, and consists of a 
telescope which turns upon a stand, and is held by a spiral spring in contact 
with an adjusting screw, by means of which the axis of the telescope can be made 
to rest at any angle to the deck of the ship. 
Fig. 16 . 
