2 
CORRECTIONS FOR QUICK TARGETS. 
Let (xbea gun, commanding a channel, whose general direction is 
F F '; let P be a distant point in FF' and let GAP be a right angle : 
then the range of a ship, steaming from PboA, would gradually 
diminish, until it reached its smallest value, at A. If the speed of the 
Fig-. 1. 
ship and the distance G A be known, corrections for range, for all 
points of the ship’s course, can be laid down beforehand for any given 
conditions of firing. 
Let v be the velocity of the ship, in yards per second, let t be the 
time, in seconds, made up of the “ time of firing” of a certain fort, 
and the time of flight, due to any range GP, when using a certain 
gun; also let 1c, measured in yards, be the range correction for travel, 
at P, under these conditions. 
Then 
' = t xv cos GP A, 
-/rv P ^. 
X GP’ 
( 1 ) 
now if GP be drawn to a scale of “ equivalent times,” 1 t will vary 
directly as GP, 
hence h = Mv x PA, where If is a constant. 
1 See Table I. 
