OF PROJECTILES. 22Z
mortars, must be founded on theory, and derived fromscience (142, 231); consequently the generality of bombar-diers are very ill-qualified for this service: but from thesmall number of officers, there being freqently a necessityduring a siege, of leaving the direction of mortar batteriesto the bombardiers, a particular form of instruction has beenexpressly made out for their use, calculated for unscientificmen, that they may be enabled to do their duty with pro-priety and effect. For this purpose the use of shells is re-duced to two principal cafes ; (229) the first consists in dis-mounting the enemy’s artillery, destroying buildings, settingfire to and overturning works, and causing disorder amongtroops : the second, in breaking through casemates that havenot been properly constructed,
233. It is sufficient in the first case (232) that the shellsbe projected with justness, without much regard to theforce of the shock ; this may be attained by observing thefollowing instructions, which are within the comprehensionof every man. The bombardiers should practise with 13and jo inch mortars of the common construction; after-wards with some of the same calibre, but with chambers ofdifferent dimensions, in order to convince them that a dif-ference in the size of the chamber considerably affects thelength of the range.
1. They should know the elevation that gives thelongest range, when the chambers are filled ; and alsothe best elevation and charge scr firing from the batteriesconstructed in the first and second parallels, when thebesieged town and the batteries are in the fame plane.
2. They should be made to observe that a differencein the form of the chambers in mortars of the famecalibre, induces a necessity of altering the elevation,and also affects the range ; and that with the samemortar, the ranges diminish in proportion as the eleva-tion is greater or less than that which gives the longestrange.
3 ; They should be taught always to load the mor-tar in the same manner, when the same charge is used ;since to negligence or mistake in this particular, maybe attributed many of the varieties that occur in thelengths of ranges: and that with the same charge,the error that may tend to shorten the range, will notgdd much to the deflection of the shell.
P 4, As