ARTILLERY IN COAST DEFENCE. 
475 
one degree, can be ascertained by watching the graduated arc of the 
depression range-finder. 
These corrections can also be conveniently noted on a ruled form 
as :— 
L. 
R. 
L. 
R. 
Wind . 
10 
Length. 
60 
Time of flight 
45 
Nett total. 25 L 
To take an instance, suppose a battleship broadside-on (300 feet 
long) passes from L to R over one degree in ten seconds ; range 3000 
yards; wind from left to right requiring 10 minutes to counteract it ; 
150 x 12 
then 10 minutes L are required for wind ;-——-= 60 minutes L are 
oO 
required if we wish to hit her in the centre; and from the table 45 
minutes R to correct for time of flight; or a nett result of 25' Left. 
As the service dial can only signal in quarter-degrees this would be 
signalled as half a degree. It may be remarked that a very rough 
approximation would be sufficient in engaging so large an object as a 
battle-ship, unless we wished to attempt the destruction of a definite 
portion of her ; since if she is end-on only wind correction is required ; 
and if broadside-on, and in motion, the corrections for length and for 
time of flight will approximately cancel each other. 
The corrections, both to range and to deflection, can only be looked 
upon as approximations; the only way to get good shooting is to care¬ 
fully observe the result of each shot, or salvo, and make corrections 
accordingly. Many circumstances which defy calculation, such as 
refraction, which causes the object to appear, and the guns to be laid 
(with tangent elevation) too high, and other atmospheric conditions, 
affect the shooting; so that the first shots must always be regarded in 
the light of trial shots. If the corrections above treated of are pro¬ 
perly made, the error cannot, however, be very great; and in cases 
where, from the enemy’s smoke or other causes, the observation is 
difficult, unless they are made there can be no chance of hitting the 
object; in any case the nearer the first shot falls, the easier it will be to 
observe and correct the error. 
The error in range can be measured by the depression range-finder, 
the range being taken to the splash of the shot, the difference between 
this and the range of the ship at the same moment being the correction 
to be applied for the next round. It has been suggested that this 
correction may be automatically made by bringing the cross-wire on 
the splash, and making the horizontal wire cut it by sliding the ful¬ 
crum in or out, without altering the range; then, bringing the wires 
back on to the object by the drum, a new range will be found—which 
will be the corrected range. This would give good results at a 
stationary object, but if the tidal error or a large powder error enter 
