80 
Minutes oe pkogeedings of 
then to be set up at fixed distances apart, and parallel to the ascertained 
prolongation. For the first gun rhe distance is equal (at least) to the 
thickness of the upper part of the parapet of the work to be enfiladed 
plus half the 50 per cent, lateral spread. The remaining lines of direc¬ 
tion are placed at intervals of 7 metres apart, provided the construction 
of the battery allows of it. 
In order to get the prolongation of a line that has to be enfiladed, we 
choose a time of day when the various lines of the work can be made 
out by the contrast of light and shade. An exterior slope of a parapet 
is thus caught by the eye, and we then change our position until the 
slope appears a line and its crest as a point. The spot where this is 
the case is on the required prolongation, and is marked by two strong 
pickets. 
The correct prolongation of a line that has to be enfiladed requires 
considerable practice, and is especially difficult if the work is well 
defiladed. The planes of alignment of the different guns are marked 
out by pickets in the central lines of the embrasures converging on 
the crest of .the work to be bombarded. These pickets are set up 
vertically—the shorter one at the outer edge of the embrasure, the 
longer one at least a metre from it. 
In order to determine the planes of alignment for converging lines 
of fire we must, by the help of a plan, fix the point of the cover over 
which the trajectory is to pass. If, then, the inner and longer picket 
is set up in the line joining the centre of the platform and the point in 
question, the outer or shorter picket has, by means of the plumb-line, 
to be fixed in the vertical plane passing through the inner picket and 
the point of the cover that the shot has to pass over. Where this is not 
practicable we have to determine by geometrical means how much the 
outer picket must be moved laterally from the parallel alignment. 
In order to align the gun on these pickets we must first mark the 
pivoting-point ( Drehjmnkt ) of the gun on its upper surface by a cone of 
cobbler’s wax, 1 to 2 c.m. high, which is moved to and fro along the 
line connecting the two sights ( Visirpunkte) and therefore in the plane 
of symmetry of the piece, until its axis lies exactly in the vertical plane 
passing through the axis of the axletree-arm. This plane is marked by 
two plummets, which are held right and left of the gun in such a 
position that the plumb-lines intersect the central line of the axletree. 
With the help of this pivoting-point the gun is moved till its plane 
of symmetry coincides with the vertical plane of alignment given by 
the plumb-line and the two pickets. The index-plates are then let 
down, and the zero-points marked on the platform. The trail is then 
moved to the right as far as is necessary to give the correction for the 
derivation, and, lastly, the directing plates are fixed in position. 
In the succeeding shots the direction, and whatever correction may 
at the time be necessitated by the wind, are given by means of the 
aligning apparatus only. 
Laying by means of pickets and plumb-line is very roundabout, and 
at long ranges is the occasion of considerable lateral spread. This 
kind of laying is therefore to be looked upon as merely a make¬ 
shift for the first trial shot. It can, moreover, be altogether dispensed 
