190 
COAST DEFENCE. 
round. It is only a repetition, with modern guns, of Lieut. Koehler’s 
experience with S.B. guns and his depressing carriage during the 
defence of Gibraltar in 1782. Drink water, the historian of that 
memorable defence, records that “ as to the accuracy of the depressing 
shot, no further proof need be adduced than that out of 30 rounds 
28 shots took place in one traverse of S. Carlos Battery.” 
It will not, I think, be questioned that observation of fire (an 
important factor in shooting when ranging is possible) is easier and 
more accurate from a height, so that advantage need not be dwelt upon, 
but simply scored to the credit of the high site. 
The most important advantage of height is, perhaps, the help it 
gives us to ascertain ranges. You have, I understand, now been 
supplied with the depression range-finder, and are already acquainted 
with the very great value of the little instrument. If you take the 
trouble to investigate the principle of its working, and compare its 
working on a high and low site, your pains will be amply rewarded. 
Taking an average of the ranges between 1700 and 1800 yards, you 
will find that an error in the instrument (whether through defective 
adjustment or faulty manipulation) of one minute at 48 feet above sea- 
level makes a difference in the recorded range of about 56 yards at 
mean tide. Supposing a rise and fall of six feet, at high water this 
error would make a difference of 64^ yards, and at low water of about 
50. At a height of 250 feet the tidal differences practically disappear, 
and the error of a minute corresponds to one in range of just less than 
ten yards. The advantage here of high site is enormous. When you 
consider the serious consequences on a low site of an error so small 
that the bubble of an ordinary spirit-level is only just moved by it, 
then you realize the advantage of a high site if for no other than from 
the range-finder’s point of view. 
In your Drill Book, on page 57, the advantage of a high site in 
automatically correcting small errors in range is pointed out. Abroad 
height is utilized to a further extent, and it is to be hoped that we may 
soon follow the good example. Automatic sights are provided; that is 
a system of sighting by means of which correct elevation is automatically 
given by laying on the target. Such sights are not intended to supersede 
range-finders, but to supplement them at shorter ranges. It is obvious 
that the range at which an automatic sight can be used with accuracy 
depends entirely on the height of the gun above sea-level. There is 
no reason why all guns mounted at 200 feet and over above sea-level 
should not make very fair practice at average ranges, say, up to 
4000 yards, if fitted with automatic sights, and at the same time be 
independent of range-finders. Here in itself is a sufficient reason for 
the preference of a high site. Range-finders and their adjuncts may 
fail at a critical moment, and the knowledge that there is a reliable 
automatic sight to fall back on, should such disaster occur, will, 
I know, be hailed with delight by all who have had experience in the 
modern conditions of coast artillery fire. 
Sir George Clarke has instanced the value of high sites by experience 
in war in the Black Sea. Without leaving the same waters, we can 
