230 THE VALUE OF A HIGH SITE FOR COAST ARTILLERY. 
the exaggerated trajectory in B. Then X will be the point where a 
line drawn from P at the angle ft, meets the perpendicular let fall 
from B on PT. 
For practical purposes, in estimating an ‘ under/ we may consider 
PX the same, whether PT is under or over P. 
TABLE VIII. 
Values of 7 . p = 30. 
Height of Site. 
Range. 
25' 
250' 
250 
44 58 
0 t 
65 50 
500 
26 34 
69 14 
750 
18 18 
66 58 
1000 
14 2 
63 26 
1250 
11 18 
59 37 
1500 
8 47 
55 51 
In fig. 12 the trajectories* of the 3 Pr. Q.F. Gun (Hotchkiss) are 
plotted for every hundred yards up to 1600 yards, with ordinates 
exaggerated thirty times, and Table VIII. gives some values of 7 , for 
two sites of 25' and 250' respectively. 
Lines at angles ft and (ft + 7 ) for a height of 250', are drawn through 
several points, to show how small PX is, compared with PT. For 
example, if 750 yards be taken as the true range, from the two lines 
drawn through that point, viz. at 73° 18' and 6 ° 20', the value of PX can 
be found after the method of Fig. 11, on the supposition that the 
range is overestimated by 50, 150, 250, 350, 450, 550, 650, 750, 850 or 
950 yards. In the first instance the 800 yards trajectory would be 
* These trajectories were plotted from the well-known formula H=16t (T-t ); the 
points of quarter, half and three quarter time were found, and were taken as *32, *58 and 
•78 of the range, respectively. It may be noticed that these sets of points, respectively 
lie on three ellipses, which pass through the muzzle, O, touch the horizontal through O at 
O, and have their major axes coincident with the perpendicular through O. It would 
thus be possible with very fair accuracy, to interpolate other trajectories, between those 
given in fig. 12. 
