4 
CORRECTIONS FOR QUICK TARGETS. 
of seconds. Beneath G M place a scale of equivalent ranges; these 
can he easily obtained by the use of the range table of the gun, as 
follows :— 
TABLE I. 
Bange. 
Time of 
Flight. 
Time of 
Firing. 
Equivalent 
Time. 
500 
•84 
3 
3-84 
1000 
1-54 
3 
4‘54 
1500 
2-36 
3 
5*36 
2000 
3*2 
3 
6-2 
2500 
4-07 
3 
7-07 
3000 
5 
3 
8 
3500 
5-96 
3 
8-96 
4000 
6-98 
3 
9-98 
4500 
8-14 
3 
1174 
5000 
9-34 
3 
12-34 
Now, in the particular case of an objective steaming down the line 
L G, equation (1) would take the form, 
k — v t ..(2) 
and if the speed be 20 knots (viz., 10 yards per second) 
k == 10 t 
Then, if we give to k the successive values of 12|, 374, 62J, 87 J, 112J, 
&c., we can at once write down the corresponding values of t, which 
are, of course, 1*25, 3*75, 6*25, 875, 11 *25, &c. 
Next, mark off these values along di by the successive points, 
Pd Pq) P 3 > Pi> P 5 ) ^ G ‘) then we see that when the objective is between 
G and p t no correction is necessary ; between p x and 25 yards is the 
correction ; between p s and p s , 50 yards ; between p s and y> 4 , 75 yards; 
between and p 5 , 100 yards, &c. The equivalent ranges of these 
points can be determined from the scale of yards below G M. 
Now, suppose the same objective to be moving parallel to L G, along 
the line PA, whose perpendicular distance from it is 1500 yards ; then 
if A be the point of minimum range, its position in GM can at once 
be determined, for, as we see in Table I., 1500 yards corresponds to 
5’36 seconds, and PA can be drawn as shown. Through the points 
Pd Pz) P$) &c., draw the lines y> 3 j?/, p%p Q ', &c., parallel to GM, and 
cutting PA, in the points a, b, c, &c., then, as we saw above, there 
will be no correction between A and a; 25 yards between a and b; 50 
between b and c; 75 between c and d; 100 between d and e, etc. If, 
now, a compass be pivoted at G, the distances Ga, Gb, Gc, Gd, etc., can 
be read off, along the yard scale on G M, and registered. 
Next, suppose the gun to command a certain channel, which is 
bounded by lines, whose perpendicular distances from G are 1500 yards 
and 2500 yards respectively. Then PA will represent the nearer 
boundary. From G, along GM, set off GB, equal to 7*07 seconds. 
