78 
MINUTES OF PROCEEDINGS OF 
and as the mean angle of jump may be taken as 6' the angle of eleva¬ 
tion will be 5° 15'. 
From the practice tables we find that at the distance of 758 metres 
the elevation with 1*2 k.g. is 4° 56', and with 1*1 k.g. 5° 28'. The 
first angle is too low and would cause the covering parapet to be 
struck. We choose, therefore, the next larger angle of 5° 28', and the 
corresponding charge of 1*1 k.g. 
We could at once employ this angle if the object was at the same 
level as the muzzle. As, however, it lies below it, the shot would pass 
over it with 5° 28'. This angle (0 — A) must therefore be reduced by 
the ground angle %. 
tan n 0 = ~ = 0*001847, - 
~ 758 
n 2 = 6'. 
Consequently, the elevation to be given (</>) is 5° 22'. 
12. The Method of Laying the Cun; Observing the Effects 
of the Fire ; Correcting the Laying. 
Since, when using curved fire, we cannot lay directly on the object, 
and as, in most cases, the tangent scale can only be employed (if at all) 
against very slightly marked auxiliary points of aim, the operation of 
laying the gun in this kind of fire requires particular attention, and 
the employment of a special aligning apparatus {Richtvorricldung ). 
Although it is easy to give the necessary elevation ( Hohenriehtung) 
correctly by means of the quadrant, still the line of direction ( Seiten- 
richtung) and the alteration of the point of impact in a lateral direction 
offer considerable difficulties, unless the guns are provided with the 
aligning apparatus for curved fire. 
This aligning apparatus consists of two index plates and two directing 
plates. 
The index plates are attached by hinges, the one to the axletree of 
the gun-carriage, the other to the trail, in such a manner that the zero- 
points of both plates lie in the plane of symmetry of the gun. In 
aligning the piece these plates are let down on to the platform; when 
the gun has been laid they are turned up again and made fast. 
The directing plates are fixed by wooden screws to the platform 
in such a manner that (taking into account the “ derivation ”) whern 
the gun is laid on the object, the similar edges of the directing 
plates coincide with the zero-points of the index plates when the latter 
are let down, and are at right angles to their lowest edges. The 
straight line passing through the longitudinal edges of the directing 
plates is called the “ directing line A 
Since the index plates are furnished with a divided scale on both 
sides of the zero-point, the gun can easily, by their means, be either 
moved laterally to whatever amount may be required, or be retained in 
any particular position. 
If the direction marked by the directing line is the required one the 
