AUTOMATIC SIGHTING. 
275 
fixed at H; the other end being attached to a fixed part of the 
mounting. A spiral spring K enclosed in a box presses the lever 
G E upwards, and thus keeps the chain taut. It is evident from this 
arrangement that as the trunnions on which the gun revolves are behind 
the fore sight, if the gun is elevated the chain pulls down the lever 
G E, and with it the point of the sight D. This as far as sighting is 
concerned is the same as if the tangent scale was raised. The amount 
the point D is depressed for any given movement of the gun is 
governed by the position, length and shape of the end of the arm GE. 
This is arranged to suit the height of the gun above the sea-level, so 
that the condition given in Fig. 1 may be fulfilled. That is the act of 
laying the sight on any object on the sea-level, brings the gun to the 
right quadrant elevation to hit that object. To allow for rise and fall 
of tide, or variation of powder, the end of the chain attached to the 
fixed portion of the mounting is capable of being moved up and down 
by a milled headed wheel, on which was engraved yards over or under, 
and feet scale, of rise and fall of tide. The officer in charge could 
thus without stopping or interfering with the layer alter the shooting as 
he pleased to meet the variation of the day. 
The problem of automatic sighting, applied to the carriage with no 
recoil to take into account, is, I think, a simpler matter, and more 
easily admits of the application of telescopic power. As to the best 
telescope, I have no hesitation in saying it should be one with very 
low magnifying power and large field. After a good deal of difficulty I 
have managed to obtain such a telescope. 
In conclusion, I trust I have sufficiently explained automatic 
sighting to allow of the principle on which it is based being understood 
and at the same time pointed out the danger of supposing that they 
can take the place generally of the present methods of laying guns. 
