18 
MINUTES OF PROCEEDINGS OF 
(2) For example, let G be the muzzle of a gun 4 ft. above tbe plane, 
and b a small object also 4 ft. above tbe plane at 1000 yds. distance. 
R R' 
Then the elevation E for 1000 yds. by the Tables will cause the shot to 
strike the ground at R, 4 ft. vertically under b, and if we want it to strike b 
we must give it some elevation E r due to a greater range R r ; but if the 
tabular elevation were the angle EGR instead of the angle EGR, then 
because there is no sensible difference between EGR and E'Gb, in other 
words, because the second intersection of the trajectory with the line of sight 
is at the same distance from the muzzle whether this line be slightly inclined 
like GR or level like Gb, then it would be sufficient in each case to direct 
the line of sight on the object, and to give the tabular elevation above it. 
(3) There are three ways of conducting the experimental practice at 
the School of Gunnery upon which our Tables are based :— 
First. —The gun is on a travelling carriage on the sands, and the elevations 
given by tangent scale above a mark of the same height as its own axis, 
viz. 3 ft. 6 in. to 4 ft. 6 in. 
Second. —The gun is on a naval carriage with the axis 8 ft. above the 
sands, and the elevations are in this case also generally given by tangent, 
above a mark of the same height as the axis. 
Third. —The gun is on a garrison or other carriage with the axis about 
17 ft. above the plane, and the elevations are either given by spirit-level, or 
given by tangent above a mark of a known height at a known distance. 
In either case the elevation recorded is that given by the tangent scale or 
the quadrant as the case may be, and the range recorded is the distance of the 
first graze on the sands. 
The following Table of 40-pr. practice under all these different conditions 
will shew how variable the results are when erroneously referred to these 
nominal elevations instead of the true elevation. 
have a line of metal elevation of 6', it might be used, and it would then be exactly consistent with 
the definition given above, 
“ Le premier point de rencontre de la trajectoire avec la ligne de mire £tant tr&s rapproche de la 
pi&ce, on n’a pas a s’occuper du tir sur un but situe entre ee point et la bouche. 
“Le second point de rencontre de la trajectoire avec la ligne de mire se nomme but en blanc, et sa 
distance a la piece portee de but en blanc. 
“ Quelle que soit l’inclinaison de la ligne de mire naturelle en dessus ou en dessous de l’horizon, 
dans les conditions ordinaires du tir, la joortee de but en blanc reste sensiblement la meme. 
Cependant, ou appelle plus specialement jportee de but en blanc la portee obtenue quand la ligne 
de mire est horizontale. 
“ Cette portee est de 500 m. pour le canon de 4, raye, de campagne. 
“ Ainsi, pour atteindre un but place a 500m., il faut pointer directement sur ce but par le fond 
des crans de mire de la culasse et du bourlet.”— Reglement, $c., p. 91. 
