307 
A METHOD 
OF 
CONCENTRATING THE FIRE OF A GROUP OF GUNS LAID 
FOR DIRECTION BY GRADUATED ARCS. 
BY 
MAJOR A. 0. HANSARD, R.A. 
(Instructor in Gunnery). 
It is well recognised that all the projectiles from a group of guns 
should strike a ship about the same spot, if possible; and it is obvious 
that, with any system where the guns are laid for direction by the grad¬ 
uated arcs (these arcs being oriented alike), the points of impact will 
be at the same distance apart as are the guns. 
Probably with Position-Finding Groups some means will eventually 
be introduced to get over the difficulty, such as a separate training 
dial for each gun, but it must take a considerable time before all such 
groups are so supplied, and in the mean time the method here des¬ 
cribed has been tried and found to answer its purpose; and as it does 
not involve any alteration to existing fittings, and does not require 
any apparatus of an expensive nature, or beyond the capacity of any 
artificer to construct, it is hoped that others may be induced to try it. 
The means to be provided consist of a diagram for the Group Officer, 
showing at a glance the number of minutes deflection to be given to 
concentrate the fire; and deflection bars, with movable pointers, to fit 
into the socket for the bolt at present supplied for reading the train¬ 
ing. 
Before describing the mode of construction of the diagram it is ne¬ 
cessary to investigate shortly the problem involved. 
In Fig. 1, A 1 A 3 and A s are the positions of the pivots of three guns 
fought by one Position-Finder; O is the point it is desired to hit. 
The pivots are supposed to be in one line, and the distances between 
them equal. 
If correctly laid the line of fire of A 2 will pass through 0, but that 
| of A : will pass through O x and that of A 3 through 0 3 . In order to 
bring the lines of fire of the outer guns through O, corrections equal 
6. VOL. XX- 
