10 
MINUTES OF PROCEEDINGS OF 
their lire—those on the left firing at the right half of the horizontal 
cut, and those on the right at the left half. 
The distance apart at which the groups of hits should be placed 
depends on the nature of the scarp and the final velocity. If the 
former is very strong, or the latter small, the centre of each group 
should be, at the most, only one metre from the next, thus ensuring 
that every shot shall strike a portion of the scarp which has already 
been loosened by the preceding ones. In the case of a weaker scarp 
or a greater final velocity the hits may be placed at 1J to 2 metres 
apart; but we must then, in repeating the fire, endeavour to make the 
shots strike the spaces left between the funnels. 
If the line of fire is oblique it is best to commence at the side of 
the intended breach that lies nearest to the battery, and to shift the 
groups of hits in succession towards the obtuse-angle. 
When the correct laying has been obtained the elevation employed 
in making the horizontal cut is to be retained unaltered, except in the 
case of a very oblique line of fire, and the only correction to be made 
will be what may be necessitated by atmospheric influences. It must 
also be remembered that, with an oblique line of fire, changing the 
direction laterally alters the range. Thus, at Strasburg, in 1870,* 
owing to the oblique line of fire, the distance of the left extremity of 
the breach in Lunette No. 50 from Battery No. 8 was greater by 
11 metres than that of the right; consequently, in working the hori¬ 
zontal cutting from right to left, the elevation had to be increased in 
proportion, and vice versa. 
The formation of the vertical cuts is not to be commenced until it 
becomes certain that the horizontal cut has penetrated the full depth 
of the scarp for the whole extent of the breach; and this may be 
known by the earth bursting out along the whole length of the cut. 
If we cannot satisfy ourselves on this point by direct observation we 
must judge of it by taking into consideration the strength of the scarp, 
the line of fire, the final velocity, and the striking power of the pro¬ 
jectiles, on the basis of the points particularly to be observed which 
are treated of more fully in part 12. The vertical cuts should be made 
as close as possible to the counter-forts, just as in the case of direct 
breaching. 
We can either employ half the guns for each vertical cut, or concen¬ 
trate the fire of them all on one end only. The first shot is directed on 
a point 1 to 2 metres above the horizontal cut, the succeeding ones are 
aimed in the same manner, and when their effect is judged to be suffi¬ 
cient ( i.e ., when the scarp is completely cut through) the point of impact 
is moved higher up. At Strasburg it was found best, instead of com¬ 
pleting the cutting, to finish about four metres first, and then make a 
similar cut at the other end, afterwards completing the cuts alternately 
up to the cordon. 
It is also recommended that heavier charges should be employed 
as the vertical cut increases in height, because time is thereby saved; 
the elevation being arranged to correspond with the altered position 
Von Decker, Mittkeilung uber die Amvendung des indirecten Sckusses. 
