ARTILLERY IN COAST DEFENCE. 
473 
able to either a standing or moving object. When the object is in 
motion, there is yet another correction to be made; this is due to the 
travel of the object, during the time which elapses between the moment 
when the drum-reader calls out the range, and the fall of the shot on 
the water. This time is made up of : first, the time lost in passing the 
range from the instrument to the group dial; second, the time lost 
between the G-roup Officer’s command to “ commence firing ” and the 
firing of the gun; and, lastly, of the time of flight. The first two times, 
which are included in the term “ time of firing,” will vary according 
to the facility with which the range can be passed to the groups, and 
also according as the guns are laid by tangent or quadrant elevation ; 
but for a given method of laying in any work, they can be made, by 
good drill and practice, very nearly constant; and having once been 
ascertained, this “ time of firing ” must be always adhered to. The 
time of flight, of course, varies according to the range. 
The actual distance travelled by the object during the time in ques¬ 
tion is not important, what we want to know is, by how much the 
range is increased or diminished during that time. 
This can be ascertained by watching the dial, and taking the number 
of seconds which elapse while the range changes by 50 yards. Sup¬ 
pose, for instance, that it is observed that the range is altering 50 
yards every eight seconds, and that the time of firing is three seconds, 
and the time of flight for the range is five seconds; then a correction 
has to be made for the alteration of the range during eight seconds, 
and as this alters 50 yards in that time, 50 yards will be the correction 
to be made. If the range altered 50 yards in four seconds, a correc¬ 
tion of 100 yards would have to be made; and if it altered 50 yards 
in sixteen seconds, a correction of 25 yards would have to be made. 
The correction must be added if the range is increasing; subtracted if 
decreasing. Tables are made out to show the corrections at various 
ranges. Separate tables are required for case I. and for case II.; the 
“time of firing” being different in each case. 
The explanation of these various corrections to the range takes 
some time, and it may, therefore, appear as if much calculation was 
involved; but, as a matter of fact, with a little practice the application 
of them is easy. 
Before an action commences the Fire Commander will know by 
what means his guns have to be laid, and consequently whether the 
correction for tide will be necessary or no. If so, he will have also 
ascertained the state of the tide; then, as soon as his object is indicated to 
him by the Section Commander, and its range approximately obtained, 
he can by reference to the table see the necessary correction. He 
will make a correction for powder, either as the result of observation 
of previous rounds or for the first shot by an estimate. He will also 
make a correction for the length of the vessel, which need be only 
approximate. Lastly, he will observe the rate at which the dial is 
changing, and make a correction for “ time of firing.” It is con¬ 
venient to have a note-book ruled in columns as follows ;— 
