ARTILLERY POSITIONS AND SCREENING GUNS. 
71 
on the sea-level. I examined the south-west corner of Wicklow and 
proposed the Glen of Imaal, where the Slaney has its source, and 
another valley to the south of it, as forming ideal ranges. Targets 
can be placed on the front crest and reverse slope of the hills; so can 
the batteries, and every variation of plunging or upward fire can be 
employed. I am glad to say that there is now a good chance of 
this site being acquired (vide Annual Report on practice just issued). 
The Position on the Forward Slope. 
The British 15-pr. gun, on its present carriage of Mark II. pattern, 
cannot fire up hill at long ranges when on the forward slope. 
To do any damage to an enemy above you, you must withdraw your 
gun either to the crest or to the reverse slope. 
The maximum elevation which the Mark II. 15-pr. carriage is 
capable of giving to the gun is only 14 degrees 20 minutes on level 
ground, as measured by me with the clinometer in the barrack square. 
The newest hand-book gives this as 16° for Mark I. and II. carriages 
(see p. 16 of 15-pr. hand-book of 1896). But later on (see p. 84) the 
maximum elevation, an given at foot of range table, is 14° 36' for 5500 
yards. 
To find out what is the maximum height at different ranges which 
the shell can attain when the gun is'on a forward slope of 5°, I have 
prepared the accompanying section. See Fig. 5. I proceed as fol¬ 
lows :— 
If I am firing from a position on a forward slope of 5° = 1 in 11,1 
must, of course, deduct this 5° from the maximum quadrant elevation, 
which the Mark II. carriage is capable of giving to the gun when 
on the level. Thus :— 
Maximum elevation is. 14° 20' 
Deduct forward slope of ... 5° 0' 
And I get the corrected maximum elevation... 9° 20' 
I can then find the height at any range. Take, for instance, a range 
of 3,500 yards. Can I fire at an object 600 ft. above me ? First , 
draw a line to scale to represent 3,500 yards on the level. Erect a 
perpendicular, measuring 600 ft. at one end of the line, join the top 
with the firing point at the other end of the line. 
Measure the angle of sight on the section of the triangle so found. 
This is found to be 2° 10'. 
Deduct this from 9° 20', the corrected maximum elevation for a 
forward slope of 5°, and we get:—• 
Corrected maximum elevation is. 9° 20' 
Deduct angle of sight . 2° 10' 
And we have an elevation of . 7° 10' 
But 7° 10' is the elevation for 3,575 yards with the 15-pr. on Mark 
II. carriage. 
Therefore, we find that the shell will reach an object 600 ft. above 
the gun and 3,500 yards off. 
Proposed 
Irish land 
range. 
The position 
on the for¬ 
ward slope. 
Latest 
carriages 
allow of ^in¬ 
sufficient 
elevation. 
Especially 
on the for¬ 
ward slope. 
Example of 
15-pr. on 
Mark II. 
carriage. 
