2023 CONSIDERATIONS ON THE SUBJECT OF TRAJECTORIES. 
jets of water under uniform pressure and capable of being inclined at 
any desired angle. 
lor purposes of tangent elevation the lower of the two intersecting 
trajectories would be taken, and for any point, the angle of tangent 
clevation will be the difference between the angle of sight and angle 
of quadrant elevation or depression of the trajectory passing through 
that point. To trace changes in tangent elevation due to firing up or 
down hill for a given range, describe a semicircle at that range and 
ascertain and compare tangent elevation for any number of points in 
its circumference. If semicircles be described at various ranges, the 
line or curve of maximum tangent elevation corresponding to range, 
may be ascertained. Similarly a range table shewing tangent elevation 
can be constructed for any desired angle of sight. Also a range table 
can be constructed for a fixed height above sea-level, 7.e., for the 
different angles of sight corresponding to the various ranges, In this 
case the intersections of the trajectories with a horizontal line below A 
would be taken. 
For ordinary cases of fire at angles of sight varying from the 
horizontal to an extent likely to be experienced in mountain warfare 
etc., the undermentioned contrivance enables the required correction 
to be readily ascertained. 
A scale of degrees (according to scale) is engraved on the sliding 
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scale GH. Along IJ is engraved the number of yards corresponding 
thereto for the maximum desired angle of sight, say 30° elevation. 
From IJ to KL are drawn curves, at any desired distance, indicating 
the changes required for all angles between + 30°, the intermediate 
