438 
ORGANISATION AND EMPLOYMENT OF SIEGE ARTILLERY. 
cutting was then ascertained, and several rounds fired with the eleva¬ 
tion thus found, formed a group of hits from which the cutting was 
extended on both sides, horizontally, to the proposed breadth of breach. 
“ If it was ascertained by actual observation (from some post distant 
from the battery) that the position of these groups was correct, the 
elevating screw was clamped, and the slightly higher elevation necessary 
as the shots became further removed from the perpendicular, was reg¬ 
ulated by the quadrant, whilst the direction was obtained by the new 
pointing apparatus, which allowed of its being kept very regularly and 
uniformly, thus ensuring the contiguity of the groups of the shots.” 
1. Whenever possible, the practice should be observed from some 
convenient point, and communication be kept up with the 
battery. 
2 . The firing—as regards elevation-should be tested several times 
a day, by very slightly diminishing the elevation, so as to see 
that the crest is only being just, cleared. 
3. In the case of front fire, it will generally be best to commence 
forming the breach at the centre, and thence working to each 
extremity ; whereas, if the fire be very oblique, the horizontal 
cut should be commenced at that end of the intended breach 
which is nearest to the battery. 
4. If several guns are engaged in forming the breach, it may be 
well to commence cutting the horizontal line from each 
extremity, half the guns grouping their shots on one end of 
the breach, and half on the other, and working 1 inwards. 
5. The shifting of the group of hits right or left, as the case may 
be, can perhaps be most accurately done by using the deflec¬ 
tion scale, and maintaining the same point of aim. 
6 * A record of the correct deflection and elevation for each group 
of hits should be kept, so that when passing along the 
horizontal line a second time to deepen it, exactly the same 
laying may be obtained. 
7. The line along which it is intended to form the horizontal cut 
having been fixed, an angle of descent—just clearing the 
parapet—should not be calculated in reference to a point on 
this line, otherwise, half the shots will be interrupted by the 
covering mass; but, a spot being selected half the vertical 
spread of the gun below this line, the proper charge and 
elevation to strike this point should be found, and the tra¬ 
jectory afterwards raised this height ; in this way the “ line of 
mean vertical deviation ” will be the central line along the 
horizontal cutting.* 
^reacting The difficulty of cutting cannelures by curved fire being foreseen, 
Htion.” em ° 4 experiments were carried out on the continent to breach by destroying 
the revetment from the cordon downwards, thus gradually wasting the 
* “ In order not to lose 50 per cent, of the shots, fire at a point somewhat above the lowest point 
of impact, but with the maximum angle of descent required to reach the lowest point /’—French 
Official Text Book) 1876, Translated by Capt, Fraser , F.F. 
