CONSIDERATIONS ON THE SUBJECE OF TRAJECTORIES. 201 
(15.) Itis thought that below CB’ the trajectory of an angle of 
quadrant elevation will coincide with that of the corres- 
ponding, 2.e., the same angle of quadrant depression. 
(16.) Of the two trajectories that will pass through any point, 
one will be a trajectory corresponding to an angle above 
“y,” v.€., presumably of quadrant elevation, the other to 
an angle between + and — 90°. 
(17.) The nearer the point is to the boundary ABC the less the 
difference between the ‘angles corresponding to the 
trajectories that will strike the point. 
(18.) The farther from C and nearer 4B’ the greater the differ- 
ence, which,’along the trajectory CA, will increase from 
0° to 90° and along CB’ from 0° to 180°. 
HARIZONTAL 
~. 
£80 =50 5 
An experiment in which the conditions might be approximately 
realised, could be made by means of a small jet, or preferably two small 
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