82 
MINUTES OF PROCEEDINGS OF 
When the point of aim has been thus selected it must be fired at in 
the manner directed further on. The charge can be determined accord¬ 
ing to the instructions in part 7, but not the elevation; because, to get 
the range, some visible point must be struck, and this point is situated 
higher than the one which would be taken as the basis of the calculation 
in determining the elevation in the case of curved fire. The elevation 
is taken from the practice tables exactly as in the case of direct fire. 
If the tangent scale suffices for the elevation, its proper height and the 
deflection for the distance of the visible point of aim can be taken from 
the table corresponding to the charge to be used—if necessary, by 
interpolation. If the tangent scale does not suffice, the angle of eleva¬ 
tion is determined in a similar manner by means of the tables, and the 
ground angle of the selected point of aim added to or subtracted from 
it, according as the latter lies above or below the level of the muzzle. 
The elevation is given by means of the quadrant, and the required 
direction by the tangent scale, the cross-piece- of which is to be set at 
its greatest height and then adjusted so as to give the required correction 
for “ derivation.” 
The trial shots are commenced with this laying. In doing this we 
endeavour, with a certain number of shots, to attain a mean point of 
impact close to the selected point of aim above the intended breach. 
By the help of the data contained in the tables this mean point of 
impact can then be easily moved laterally and vertically (downwards), 
so that the first cluster of hits shall fall upon the desired point, or 
on one end of the intended breach; the tangent scale being employed, 
and the gun laid on the auxiliary point of aim. 
If we conclude from further observation that the position of this 
cluster of hits is correct, the same laying will be retained for the 
succeeding shots, the direction being given by the aligning apparatus 
by laying down and fixing the directing plates in the line connecting 
the zero-points of the index plates. The quadrant only is used in 
giving the elevation. 
If now, after thus shifting the point of impact, only a few of the 
shells, or at most 25 per cent, of them, strike the. covering mass, it 
is a proof that the charge has been correctly chosen. Moreover, under 
ordinary conditions of weather and with accurately known profiles, the 
elevation obtained practically in this manner will correspond with that 
calculated by the rules given in part 7. 
If, with the given laying, only a few shells, or none at all, strike the 
cover, it is a proof that the charge is a little too small. It may, however, 
be retained without much detriment if the final velocity is sufficient. 
If, however, more than half the shells strike the cover, the charge is 
manifestly too large and must be altered. The trial shooting must 
then be gone through over again with the new charge. 
We may be compelled, in default of a visible object of aim above 
the scarp to be breached, to fire at the crest of the intervening rampart; 
though this is a less advantageous method. There is no difficulty in 
firing at a point of this crest, because the elevation is to be looked 
upon as correct if half the shells clear the cover and half strike it. 
If, now, the information afforded by the practice tables were always 
