272 
AUTOMATIC SIGHTING. 
The above. ai*e the errors worked out mathematically. For those 
who may be sceptical on these points, the following* gives the actual 
errors of laying an automatic sight in 1 879 when tried by a committee 
of experts. The sights were laid on a steamer moving out of the 
harbour, height of battery 150 feet. 
Range. 
Error. 
Range. 
Error. 
1310 
40 
2580 
210 
2240 
90 
3140 
500 
3900 
890 
So far then as regards the error due to the unaided eye, of course 
this will be reduced if telescopic power is applied. In certain 
weathers, in fog, and with powder smoke hanging about, a telescope 
cannot always be used with advantage. 
We now come to the serious errors arising from want of level of the 
emplacement platform, etc. It must be in the experience of all officers 
who have worked with Coast Artillery how much the racers are out of 
truth, and if level to-day soon go out of truth with firing. So that 
the application of automatic sighting to the older form of guns and 
platforms is out of the question except for very short ranges. Even 
with the newer types the accuracy must bo very considerable. 
Suppose, for purposes of calculation, we take the error of platform at 
four minutes, the following table gives the error for a 6" Q.F. gun 
mounted at a height of 50 feet. 
Range. Error. 
1000 yds. -I- 12 yds. 
2000 „ or 270 „ 
3000 „ - 750 „ 
4000 „ 1550 „ 
(-f when platform is depressed). 
(*— ,, „ „ elevated). 
The method of arriving at these figures is as follows. Imagine the 
gun fitted with automatic sights to be placed on a platform capable of 
being tilted. When the platform was level, and the sights laid say at 
2000 yards, the gun would bo at a quadrant elevation of 1°. 28', that 
is 1°. 57' (tangent elevation for 2000 yards) miuus 0° — 28*6' (the 
range-finding angle). 
Now if the platform is tilted 4' down to the front it is evident that 
the gun will be at 4' less quadrant of elevation, and thus throw the 
shot 57 yards short of the 2000 yards. At the same time the line of 
sight will also have been tilted 4' down, and will cut the water at 1757 
yards instead of 2000 yards. So that when the gun-layer brings his 
sights up to the target at 2000 yards, he will be virtually elevating 
the gun to 2270 yards (see above table). We see then that a very 
slight variation in the level of the platform, causes a large error in 
the quadrant elevation, owing to the automatic mechanism. 
I think I have given figures enough to show that except, under 
special conditions, automatic sighting will not and cannot do away 
