THE BOYAli AETIELEEY INSTITUTION. 
447 
44*4 + 39*i 
-~-= 41*8 tenths of inch; or the mean angle of elevation 
LA 
f5 0 1Q ; + 7° V 
will be---- = 6 ° 38'. If we use the quadrant we must 
u 
5 .67 
deduct the ground angle of which ^ = 0*0016 is the tangent; or an 
angle of 5', since the object to be hit is below the level of the piece. 
We have, by means of the tables and the formula, learnt what the 
angle of elevation and charge of a certain piece, firing at a given range* 
should be, so as to throw its shell clear of the crest of a covering work 
and to strike the escarp wall at the proper height to make the best 
breach. Q. K F. 
When we come to consider what an advance in ballistics we have in 
this system of breaching, what saving of life there would be under such 
a system as compared with the old system of breaching from batteries 
erected on the crown of the glacis, I believe I shall have most artillery¬ 
men with me in expressing the hope that tables such as I have described 
for all guns of the siege train should be drawn up from careful practice 
carried out for this purpose; further, that similar tables for all field 
guns should be constructed, for use in shelling occupied villages and 
field fortifications. 
59 
