97 
ADJUSTABLE POINTERS 
FOR 
CONCENTRATING THE FIRE OF GUNS IN GROUPS, 
WORKED BY 
POSITION-FINDER, AND FOR DRIFT CORRECTION. 
BY 
MAJOR LATHAM C. M. BLACKER, R.A. 
THE question of being able to concentrate the fire of guns arranged 
in groups and fought by position-finders is one which has attracted 
considerable attention from time to time and serious proposals have 
been made towards carrying out this object. 
As far as I am aware no satisfactory plan has yet been devised, so I 
venture to put forward the following device of an adjustable pointer 
adapted to the purpose. In the first place there are two factors to 
consider, one is that supposing the normal case of four guns on a 
straight front under existing arrangements, when they are trained at 
the centre of their arcs, the lines of fire will be parallel and, say the 
guns are ab a minimum distance of 15 feet apart, then the line of fire 
will be 15 feet apart and the shots should strike the water 15 feet 
apart. 
i supposing the pieces are trained extreme right or left then the 
lines of fire will be found to be only about 124 feet apart. This 
difference will of course affect very accurate concentration and should 
be taken in account if thoroughly precise results are desired. 
Of course were expense no object it will be possible to devise very 
accurate adjustable pointers concentrating exactly at any range and at 
any angle of training, but except in the case of new mountings, and as 
the position-finding dials can only be read to } of degree, it does not 
seem worth while. 
The following plan provides for an inexpensive alteration to existing 
pointers whereby accurate concentration can be effected at every 100 
yards and for extreme right and left traverse. This will be found 
quite sufficient for ordinary purposes and will put an additional power- 
ful weapon in the hands of Battery Commanders enabling them to 
explode four common shell at one spot in the unarmoured part of a 
vessel if desired, this adding greatly to the fire effect of their com- 
3. VOL, XXIII. 
