192 
MINUTES OF PROCEEDINGS OF 
difference between tbe two possible ranges is always too great to allow 
of a doubt; should, however, any uncertainty exist, a second observa¬ 
tion, with a different distance between the guns, will dispel the ambiguity, 
as the real answers, in both cases, would be the only ones agreeing. 
Beyond the first, or straightforward case, this is the only point in the 
roller which it is necessary that the gunner should know; as the case 
will, however, occasionally arise, it is well to say a few words on this 
head. 
Where rapidity is required, the guns will generally be kept at one 
drill interval, 19 yards apart; or at two, 38 yards apart; in either case 
a few extra yards may be stolen by an officer wishing to have accurate 
ranges. 
The instruments are quite capable of giving the range with a 19 yards 
interval, or base, up to 2,000 yards ; yet it does not pay to make this the 
ordinary base, because the extra care required in the manipulation more 
than makes up for the disadvantages of the larger base. 
At a 19 yds. interval, or base, it is clear that the first special or small 
number case will not arise, as artillery do not care to measure ranges of 
less than 500 yds. 
In trying for a 38 yds. base, the guns may, after coming to the ground, 
find themselves as much as 50 yds. apart; in this instance, the first 
special or small number case may arise, as, with a 50 yds. base, anything 
under 1150 will fall in the small numbers, and 1100 yds. is an artillery 
range. 
Now, in this instance, if a gunner sees that the enemy are from 800 
yds. to 1500 from him, and that the interval between the range-guns is 
considerable, he ought to be on the look out for the small numbers. 
Suppose, first, that the sum of the two index angles, as found by the 
roller, or as mentally added together, equal 10 or 20, the gunner knows 
at once that he is dealing with the ordinary case, because 10 and 20 on 
line E will, in-the ordinary course, give ranges of 1140 and 1340, which 
are between the limits 800 and 1500, while 10 or 20 in the low numbers 
would give ranges of 600 or 635, which the gunner’s eyes assure him 
would be an improbable answer. 
If, on the other hand, the sum of the index angles should be 70 or 80, 
then the gunner knows at once that he has to seek for the range (in the 
instance specified, among the low numbers), because 70 and 80 will, in 
the low numbers, give ranges of 880 and 755 yds., while in the ordinary 
numbers they would give the impossible ranges of 3700 and 5700. 
To Test the Tape. 
The tape is liable to injury; as a rule, however, if the tape be set right 
for a length of 40 yds., that is, if when the axis of the angle-finders are, 
say, 41 yds. apart, the tape be made also to read 41, then it will be 
sufficiently right all through its length. 
To Correct the Tape. 
Place the guns about 40 yds. apart, laid upon an object, the guns to 
be square with each other. 
