176 
MINUTES OE PROCEEDINGS OE 
Instead of degrees and minutes on the scale for measuring the base 
angles, I employ a decimal division. Each of the range-finder’s divisions 
is equal to 1J minutes, consequently 100 of the divisions — 2J°. 
On this notation 
L 2\° 
would equal 
100 
5 9 
)) 
>> 
200 
100° 
)) 
>> 
4000 
170° 
)) 
6800 
172J° 
» 
» 
6900 
175° 
» 
}) 
7000 
177J° 
7100 
180° 
>> 
7200 
But for military purposes, it is clear that the sum of A and B or (A + B) 
would, out of 1,000 cases, he roughly— 
900 times between 177J° and 180° 
90 „ „ 175° „ 177±° 
9 „ „ 1721° „ 175° 
1 „ under 172|°, 
or in some such proportion, because if we employ a base of 40 yards— 
All Ranges over 915 yards will give (A + B) over 177J° 
* * 460 „ „ „ 175° 
300 
y> » „ „ „ 
and gunners will not measure distances at case shot ranges 
172J° 
This consideration allows a further simplification of notation, and 
instead of calling 172^° 6900 
175° 7000 
177|° 7100 
180° 7200, 
172J°, 175°, 177J°, 180°, are all alike called 100 or 0. Consequently 
the instruments only show by how much A -j- B exceeds 172J 0 , or 
175°, or 177|°. 
If A is recorded on one instrument as 85, B on the other as 90, 
(A + B) = 175, but as the roller does not deal in hundreds, it only 
shows 7 5; the hundred is omitted. 
There is then a doubt as to whether the sum of A + B 
= 177J° + 75 divisions = 179° 22' 30" 
or, = 175° -h = 176° 52' 30" 
or, = 1721° +..„■■= 174° 22' 30" 
or = &c. 
If the base be 40 yards the corresponding ranges are 3660; 740 ; 370. 
It will be seen that between the first and second values there can be 
no hesitation in practice, while between the second and third there might 
be some doubt. 
But again, in practice it is so simple to keep the base under some 
rough proportion to the range that this third value need never occur. 
