THE ROYAL ARTILLERY INSTITUTION. 
59 
tion—as may happen in the case of curved breaching or demolition 
fire—for the purpose of utilising a fixed per-centage of the lower half 
of the trajectory pencil, would, if the nearest or deepest point of impact 
were taken at the foot of the traverse (or one metre above it), cause a 
diminution of the per-centage of hits, as regards the artillery materiel 
and the personnel to be struck; because, in this case, the closest 
grouping of the enfilading shots would be at too high a level. 
If the lines to be enfiladed are provided with traverses according to 
the principles of modern fortification the angles of descent will be 
so steep that in enfilading at the shorter ranges it will be very difficult, 
even with the short 15 c.m. gun and the smallest charges, to hit the 
guns situated behind the traverses'. 
At the longer ranges of 1200 to 3000 metres, the mortar-like effect 
of the 15 o.m. gun can, in such cases, be utilised. The gams fire thus 
at an angle of. 25° or 30°, with a charge corresponding to the distance 
(as with mortars), practice tables being specially prepared for the 
purpose. 
With such unfavourable profile conditions it even appears advisable, 
before commencing the enfilade fire, to cut away the crests of the 
traverses by a systematic bombardment, using full service charges. • 
In enfilade firing, in order to endanger the communications round 
the traverses and with the lower terreplein terraces, we should bombard 
this part of the terreplein by directing on it that flank gun of an enfi¬ 
lading battery the line of fire of which lies innermost, and take the 
point of impact according to the lateral spread of the piece. The 
employment of a larger charge will, in the case of this gun, be, in 
general, possible. 
The fire of the remaining guns should be concentrated either on the 
interval between two traverses, or on that between the parapet and the 
first traverse; and as the bombardment proceeds the mean point of 
impact should be transferred to the other intervals in succession. The 
way in which the lateral spread of the projectiles has to be taken into 
consideration in the selection of the line of fire will be discussed in 
part 12. 
7. Determination oe the Charge and Elevation when the Angle 
of Descent and Distance are Given. 
In order to enable us to determine, with the help of the practice 
tables, the charge and elevation for curved fire, we must first calculate, 
according to the directions given in part 2, the angle of descent either 
for the top of the covering mass or for the lowest or nearest point of 
impact. 
We then take from the practice tables that charge which gives this 
angle of descent at the given distance. If the distance is not exactly 
given in the tables we interpolate the angle of descent between the 
next smaller and the next larger distances. If the final velocity 
given in the tables for the charge corresponding to the angle of 
descent holds out an expectation of a good result with reference to the 
capability of resistance of the scarp, then the charge to be employed 
