THE 110YAL ARTILLERY INSTITUTION. 
81 
with if there are any conspicuous objects in the plane of alignment, 
either in front of or behind the object of fire, which can be seen 
from the gun. The direction is then given by means, of the tangent 
scale, the cross-piece of which is set at any convenient height—the 
derivation being, of course, allowed for. 
In enfilading we must endeavour to find suitable elevated spots which 
will afford a view of the line to be bombarded. If we can make out 
the individual traverses from a lateral position there will be no difficulty 
in correcting the laying, since the respective columns of the practice 
tables give the necessary information, and the same rules will have 
to be observed as in the case of direct fire. The essential point is to so 
regulate the direction, according to the amount of wind at the time, and 
the elevation, that by avoiding firing too short the projectiles may 
strike the terreplein as quickly as possible. 
An alteration of the charge should only be made in very rare instances, 
because, in enfilading, the amount of curvature of the trajectory is not a 
matter of importance. If the projectile clears the covering mass it will 
be in any case more or less efficacious, provided the charge nearly 
corresponds to the required angle of descent, and is not too. large. 
If a good view of the traverses and the spaces between them, by 
means of which the laying could be corrected, cafinot be obtained, we 
must single out and fire at some fixed point, and then, by changing the 
point of impact, endeavour to attain the object of the bombardment. 
To this end we select-some point of the object that can be plainly seen, 
and on which the effect of the fire can be easily observed—usually the 
first traverse—and fire at it in such a manner that the mean trajectory 
passes through its crest. This may be looked upon as the case when 
half the shots strike the traverse and the- rest pass over it. The point 
of impact is then to be shifted, by means of the requisite change in 
the elevation and direction, to the portion of the terreplein that it is 
intended to hit. 
If none of the traverses can be properly seen, we must in the first 
instance fire at the parapet in front. 
If it is necessary to knock away the traverses in order to get at the 
guns behind them, it is a good plan to take the point of impact, not at 
the centre of the traverse, but at its innermost end. 
Ydien observation is difficult we ought, in order to avoid continually 
overshooting the mark, to diminish the elevation from time to time by 
the amount corresponding to the distance of the mean point of impact 
from the centre of the glacis, when the projectiles will visibly fall too 
short. It may be mentioned here that, owing to the slope of the 
glacis, the distance from the crest , at which the shot strikes this slope 
is generally over-estimated. 
In carrying on curved breaching or demolition fire we must, in the first 
instance (by help of a plan), take the plane of alignment through a point 
of the parapet above the scarp to be breached (in badly defiladed works 
through a point of the masonry that can be seen) so situated that the 
intended point of impact may “lie in this plane. The proper direction 
is given by laying on the visible point by the tangent scale—of course 
with the necessary deflection. 
