THE mortar is a ƒort of cannon, made of the like metal, but much ƒhorter, and wider, than the common cannon; the kind of bullet, for the diƒcharge of which this piece is generally uƒed, is called a bomb.
        The name of mortar given to this piece might, perhaps, be taken from its reƒemblance to a common mortar.
        The bomb is a great hollow bullet, concave within, which is filled with powder, and by means of the mortar is diƒcharged upon the place intended to be deƒtroyed.  Theƒe bombs produce two effects, viz. that of ruining the moƒt ƒubƒtantial buildings by their weight, and that of creating great diƒorder by their ƒplinters; for when the powder they are charged with takes fire, its effort breaks or burƒts the bomb, and explodes the ƒlinters on every ƒide with great violence.
        The uƒe of the mortar is very ancient; M. Blondell thinks they have been uƒed as long as other cannon, but is of the opinion they were then employed only in throwing ƒtones, and red-hot bullets; he thinks too that the firƒt bombs were thrown in 1588 at the ƒiege of Wachtendonck, a town in the duchy of Gueldres.  But be this as it may, they were not uƒed in our army till the firƒt ƒeige of La Motte in 1634. Lewis the 13th ƒent for Mr. Maltus, an Engliƒh engineer, from Holland, who made uƒe of bombs in ƒeveral ƒeiges with ƒucceƒs, and was killed at that of Gravelines in 1658.  He had remarked, ƒays M. Blondell, a poƒt where he deƒigned to force the trenches in the night, and being deƒirous to ƒhow the place to the general officer, he leaped into the trenches to reconnoitre the ƒituation; the general officer did the like after him, but not having well reconnoitred the place, he deƒired Maltus to jump in a ƒecond time, to remark it with more exactneƒs; Maltus conƒented, and leaping received in the air a muƒket ƒhot in the head, which made it ƒaid jeƒtingly in the army, that he was kill'd flying.
        The aperture l of the mortar (Plate V, Fig. 2) is called its mouth, the oppoƒite a, its breech; b is its touch-hole, which correƒponds to the inner bottom, or the place that receives its charge of powder; this place is called the chamber of the mortar; the two prominences c c are its trunnions, or the parts by which it is ƒupported on its carriage; d is the aƒtragal of the touch-hole, e the firƒt renfort, fthe platband of the renfort, with the handle by which the mortar is ƒuƒpended and managed, and its mouldings; g is the chace, h the neck aƒtragal, i the firƒt collar or neck, k the rim or moulding of the muzzle; the concave part of the piece, from the mouth to the mouldings of the platband, is called the bore of the mortar, and the chamber is the reƒt of the cavity quite to the breech.
 

SECT. II. Of  the Carriage of the Mortar

THE mortar is placed upon a carriage, to facillitate the uƒing of it; the design of the carriage is to hold the mortar firmly in the ƒituation it is put into, ƒo that the explosion of the powder it is charged with may not alter its direction.  The carriage of the mortar has no wheels; for a mortar is not, as the cannon, removed from place to place on its carriage.  Several ƒorts of carriages for mortars have been contrived; ƒome have been made of iron, and ƒome of braƒs; but we shall here treat of none but thoƒe commonly uƒed, which are compoƒed of two pieces of wood, more or leƒs long and ƒtrong, according to the ƒize of the mortar; theƒe, as in cannon, are called cheeks, and joined by very thick tranƒoms.  In the middle of the upper ƒide of the cheeks are two ƒemicircular notches, to receive the trunnions; over each of theƒe is placed a very ƒtrong band of iron, called the upper band, the middle of which is bent in a ƒemicircle, to embrace the trunnions, and keep them faƒt to the cheeks of the carriage.  The inward part of each notch, or hollow, is lined alƒo with the like iron band, called from its ƒituation the under band; theƒe bands are made faƒt to the cheeks, by long iron pins of great ƒtrength; the upper band is ƒometimes faƒtened to the cheeks by another band of iron, that covers each of its extremities.  The cheeks are ƒtrengthened before and behind with round bars of iron, which croƒs them from ƒide to ƒide, and ƒerve to unite more firmly one part to the other, and bind the cheeks faƒt to the tranƒoms; theƒe are called pins.  On the front of the cheeks, or carriage, are four iron pegs, or pins, ƒet up perpendicularly; between theƒe is placed a piece of wood, on which reƒts the belly of the mortar, or that part of it which contains its chamber.  This piece of wood ƒerves to ƒupport the mortar while it is fired, and is called the pillow.  Inƒtead of the iron pegs, it is ƒometimes ƒecured in a groove, made on purpoƒe, towards the extremity of the cheeks.  When the mortar is to be elevated, and its inclination on the pillow leƒƒened, the aiming wedge is introduced between the mortar and its pillow, almoƒt in the ƒame manner as in pointing cannon.  For the mortar mounted on its carriage ƒee Plate V. Fig. 3.
 

SECT. III. Of  the Poƒition of a Mortar proper for firing a Bomb, and the line deƒcribed by the Bomb during its motion.

AS one of the effects of the bomb reƒults from its weight, it is never diƒcharged in the ƒame manner as a ball from the cannon, that is, by directing or pointing the mortar at a certain object; but the mortar is a little inclined to the horizon, ƒo that the bomb being thrown up obliquely, much in the ƒame direction as a tennis ball ƒtruck by the racket, may fall upon the place intended; from whence it appears that a mortar has no point-blank range, or at leaƒt that no uƒe is made of it.
        The mortar being in a fixed ƒituation oblique to the horizon, ƒo as that the line a c, which paƒƒes through the middle of it longitudinally, being continued, would make an angle b a d, which the horizontal line a b, a bomb diƒcharged in the direction of this continued line wou'd deviate from it every inƒtant of its motion by its weight, which inclines it towards the centre of the ƒuperficies of the earth, and by this means it would deƒcribe a kind of curve line a e b, called by Geometricians a parabola. *
        Weight, or gravity, always operates equally on a falling body; for as it always ƒubƒists in an equal degree, it muƒt alƒo always act with equal force, or, which is the ƒame thing, produce always the ƒame effect at the ƒame time.  So, if in the firƒt inƒtant of falling it communicates to a body a certain force capable of moving it a certain ƒpace, in every following inƒtant it muƒt communicate a force ƒufficient to move it the like ƒpace, and by this means the velocity of a falling body is every moment accelerated; for if it has on degree the firƒt inƒtant, it will have two the ƒecond, three the third, and ƒo on.  From whence it follows, that it muƒt move different ƒpaces every inƒtant, and by that means deƒcribe the curve line juƒt mentioned.
        The line a b is called the extent of the range, or the amplitude of the parabola; and the line a d the line of projection, or direction of the bomb. Plate. V.  Fig. 3.
 

SECT. IV. Of the Method to be ufed, in order to throw
a Bomb upon a Place propofed.

TO make a bomb fall on a given place, two things muƒt be conƒidered.
        Firƒt, The inclination, or poƒition, which ought to be given to the mortar; and
        Secondly, The quantity of powder it ought to be charged with.
        We shall endeavour to give fome idea of the manner of aƒcertaining both theƒe particulars.
        Suppoƒing a mortar pointed vertically, and in this ƒituation a bomb to be fired, it will deƒcribe a line nearly perpendicular to the ground on which the mortar is placed, I ƒay nearly, becauƒe the mortar will always have ƒome little motion, which will deƒtroy the exact perpendicularity of the line deƒcribed by the bomb; but, abƒracted from this, a bomb diƒcharged vertically, or perpendicularly, would fall again into the mortar.
        If the mortar be afterwards inclined more and more towards the horizon, the bomb will fall ƒrill further and further diƒtant from the mortar, till the direction of the piece makes an angle of 45 degrees with the horizon; the more the mortar is inclined beyond or below this angle, the more the range of the bomb will diminiƒh; all which is ƒtrictly demonftrated by geometry. But the following is a very ƒimple manner of conceiving it, without having recourƒe to that ƒcience.
        A bomb diƒcharged in the direction of a line but little deviating from a vertical one, or a line perpendicular to the horizon, will fall at a little diƒtance from the place the mortar ƒtands upon; this requires no proof. A bomb thrown in the direction of a line, which makes a very acute angle with the horizon, will prefently come to the ground by its weight, and conƒequently will not, any more than the other, fall at any conƒiderable diƒtance from the mortar.
        This premiƒed, it is eaƒy to conceive that for a bomb to fall at the greateƒt diƒtance from the mortar, it muƒt be fired in the direction of a line at the greateƒt poƒƒible diftance, as well from a vertical as horizontal line, or line level with the ground; this line is that which divides into two equal parts the angle form'd by the vertical and horizontal lines, which being a right angle, that is, an angle of 90 degrees, a bomb will be thrown to the greateƒt poƒƒible diƒtance in the direction of a line making an angle of 45 degrees.
        Above the angle of 45 degrees the range will diminiƒh, becauƒe the bomb approaches the vertical line, and under this angle it will likewiƒe diminiƒh, becauƒe the bomb approaches the horizontal line.
        By this it appears, that there are two angles, according to which a mortar may be inclined, to cauƒe the bomb to fall on the ƒame place; theƒe are the angles equally diƒtant from the line which cuts the quadrant into two equal parts; ƒo that if (for example) a mortar be levelled at an angle of 30 degrees, the bomb will fall at the ƒame diƒtance, as if it had been levelled in an angle of 60 degrees, each of theƒe angles being 15 degrees distant on this or that ƒide from the middle of the quadrant, that is, from the angle of 45 degrees.
        Knowing then that a mortar levelled in an angle of 45 degrees throws the bomb to the greateƒt diƒtance, in order to throw a bomb to a given diƒtance with a given charge of powder, it muƒt alƒo be certainly known that this quantity of powder is ƒuƒƒicient to communicate to the bomb all the force it will have need of; and this is the ƒecond thing to be conƒidered.
        A bomb muƒt be fired with the quantity of powder given, in an angle of 45 degrees, and the diƒtance found by trigonometry, or otherwiƒe, from the place where the mortar ƒtood; ƒo that where the bomb falls, if this diƒtance is greater than, or equal to the diftance propoƒed, the quantity of powder with which the mortar was charged will be ƒuƒƒicient; if leƒs, the quantity of powder muƒt be increaƒed; and when after ƒome trials the proper charge is found, the mortar muƒt be charged with that quantity, and the bomb will fall at the place intended.
        After this the mortar muƒt be fixed at ƒuch a degree of inclination as is thought proper, and in this ƒituation it muƒt be fired, and the place where the bomb falls obƒerved; if the piece was levelled below 45 degrees, and the bomb does not fall ƒo far diƒtant as deƒired, the piece muƒt be a little raiƒed; if, on the contrary, it falls too far off, it muƒt be a little more inclined; and by theƒe eƒƒays the proper degree of inclination may be eaƒily and ƒpeedily found.
        If the mortar is levelled above 45 degrees, it muƒt be more inclined, ƒo as to make a more acute angle with the horizon, to increaƒe the range of the bomb; and, on the contrary, raiƒed nearer a perpendicular, to diminiƒh it; all which are conƒequences drawn from what has been ƒaid on this ƒubject.
        When the inclination a mortar ought to have to throw a bomb to a given diƒtance is found, it muƒt be fixt in that direction; and the bombs fired with the quantity of powder, uƒed in the eƒƒays or experiments juƒt mentioned, will fall pretty near the place deƒired; I ƒay pretty near, becauƒe it is very difficult always to charge a mortar exactly in the ƒame manner, and a great number of circumstances happen which alter the flight of the bomb.
            It muƒt be obƒerved,
        Firƒt, that the greateƒt diƒtance, to which a bomb can be thrown with the ƒtrongeƒt charge, is little more than about 1800 or 2000 fathom.
        Secondly, that though a mortar may be levelled, either ƒo much above, or below, 45 degrees indifferently, to carry a bomb a given diƒtance, yet when any building is to be deƒtroyed, it muƒt be levelled above 45 degrees, becauƒe the bomb riƒing to a greater height when fired according to a greater angle, falls with greater force, and by confequence will do more damage to the place on which it is thrown. But when a company of men are to be fired upon, the mortar muƒt be levelled below 45 degrees, that the bomb may not have force enough to enter far into the ground, and that the ƒplinters in the exploƒion may do more execution.
        Thirdly, that what has been ƒaid of the flight of bombs is applicable alƒo to cannon, the ball of which will go furtheƒt when diƒcharged in a direction neareƒt an angle of 45 degrees.
 

SECT. V. Remark on the foregoing Method of throwing Bombs.

THE method of finding the inclination or poƒition of a mortar, as laid down above, is entirely mechanical; and the art of throwing bombs, which may be ƒaid to be now arrived at its higheft perfection, would yet be very imperfect and trifling, if there were no other methods of finding this direction. But there are rules for doing this with much greater exactneƒs, and by which the fitteƒt direction of a mortar may be found at once, without making any previous eƒƒays. It is however true, that the exactneƒs of the theory is ƒcarce ever anƒwered in practice.
        For although the theory gives rules for throwing a bomb without tryals upon a given place, yet experience does not always correspond with thoƒe rules, by reaƒon of an infinite number of accidents, which cannot altogether be prevented. But theƒe rules are not therefore uƒeleƒs, they anƒwer the end propoƒed more ƒpeedily, and they alƒo furnish principles and methods of perfecting practice. We ƒhall not treat of thoƒe rules in this diƒcourƒe, becauƒe they are founded upon ƒeveral geometrical propoƒitions,which are unknown to the greateƒt part of thoƒe for whole uƒe this work is intended, and they may be found in moƒt treatiƒes of geometry and mechanics.
        When bombs were firƒt uƒed, it was quite neceƒƒary to determine many things by eƒƒay, becauƒe principles and a more exact method were wanting. But it muƒt appear very ƒingular, at the time when M. Blondell, master of the mathematics to the Dauphin, and field-marƒhal and general of the king's forces, had compoƒed an excellent treatiƒe on the art of throwing bombs, that M. St Remy, who was not a stranger to that performance, should ƒtill apologize for eƒƒays,
        "It ƒeems, ƒays this author, alluding to the principles and theory of M. Blondell, that 'tis better ƒteadily to follow thoƒe who are in the continual exerciƒe of bombs, and who find by experience their method to be good, becauƒe experiments, and eƒpecially thoƒe made with gun-powder, are always of more weight than the moƒt learned obƒervations."
        There is a wide difference between the sentiments of the preƒent day, and thoƒe of the time of M. St Remy, with reƒpect to artillery. Practice has now all the attention which it merits, and at the ƒame time the theory is not neglected; and hence it is that practice is brought to great perƒection, and, as we may preƒume, will ƒtill be rendered more perfect. To this improvement the artillery ƒchools eƒtabliƒhed by the king will without doubt contribute; theory and practice go there hand in hand, and receive mutual aƒƒiƒtance from each other. Nothing can exceed the order and eƒtabliƒhment of theƒe fchools, and every thing may be hoped from the ability and merit of the officers placed at the head of them, and from the knowledge which there is in general among the gentlemen of the artillery.
 

SECT. VI. Of the different Kinds of Mortars.

THere are mortars of different ƒizes, as there are cannon; ƒome have cylindrical chambers, which they call mortars of the old faƒhion; ƒome have ƒpherical chambers, others chambers in the shape of a pear; theƒe are in the new manner; and, laƒtly, there are others with chambers shaped like the ƒruƒtum of a cone.

The mouths of mortars are from 6 to 18 inches diameter, the chambers are bigger or leƒs according to the ƒize of the piece, and they contain from 2 to 12, and even to 18 pounds of powder. In Plate VI. and VII. may be ƒeen different mortars with their chambers.

The mortar a (Plate VII, Fig. 2) is 4 feet 4 inches high, all its cavity is marked by a pricked line; the narroweƒt part of this cavity, which lies neareƒt to the breech, is the chamber of this mortar, and is in the ƒhape of a pear; the mouth or aperture of this chamber begins at the moulding of the renƒort, and is 5 inches and an half diameter; the chamber is 13 inches long, and 7 and an half diameter in the middle; it contains 12 pounds of powder. The trunnions of this piece are 32 inches from point to point, and 9 in diameter: the bomb it diƒcharges is 17 inches 10 lines diameter, and its thickneƒs, which is included in this diameter, is every where 2 inches, except the part on which it reƒts in the piece, which is 10 lines thicker; it contains about 30 pounds of powder, and it weighs 520 pounds when charged.

The mortar b (Plate VI. Fig. 3) has a ƒpherical chamber, which contains 18 pounds of powder; the bore of this mortar is 12 inches and an half diameter at its mouth, and its length is 18 inches and an half; its chamber is 9 inches and 7 lines diameter, its aperture, or neck communicating with the upper cavity, or bore, 6 inches diameter, and 4 inches long; the trunnions of this piece are from point to point 31 inches and an half, and 8 inches diameter. Its height is in all 3 foot 5 inches one third; the bomb it carries is 11 inches diameter, it contains 15 pounds of powder, and weighs about 130 pounds.

Figure 4. Plate VI. is the ƒection, or profile of another ƒpherically chamber'd mortar, the height of which is in the whole 3 foot 2 inches, and the length of its trunnions from point to point, is 30 inches, and their diameter is ƒeven.
This figure ƒerves chiefly to ƒhow the little chamber c(3) of the the depth of one inch, or thereabout, and two inches in diameter, which is made at the bottom of the bore of the mortar, much in the ƒame manner as in the pieces of cannon called 24 and 16 pounders; the pipe of the touch-hole terminates in the bottom of this little chamber, and is bored in a piece of copper, as thoƒe of cannon, in the ƒhape of the ƒruƒtum of a cone inverted. This metal is about an inch and an half diameter in its upper part, and two inches and an half at the bottom; its uƒe is the ƒame as in cannon, to reƒiƒt the effort of the powder with greater force than the metal of the piece, and by conƒequence preƒerve the touch-hole.
        Fig. 1, and 2 in Plate VII. repreƒent two other mortars. The firƒt e is a ƒide view of a cylindrically chambered mortar; it throws a bomb of 11 inches and two thirds, its bore is 12 inches diameter at the mouth, and 18 deep, its chamber is 9 inches and an half long, and 5 inches and a quarter diameter, and contains 6 pounds of powder; the trunnions of this mortar are 28 inches long, and 8 in diameter.
        The ƒecond figure f in the ƒame Plate VII. is a ƒpherically chambered mortar, which, as well as the preceding, throws a bomb of 11 inches two thirds. It is 12 inches and an half diameter at its opening or mouth, not including the thickneƒs of the metal. The depth of its bore is 18 inches, its chamber is 8 inches two thirds long, and ƒeven in diameter; it contains 8 pounds of powder, its trunnions are thirty inches long from one end to the other, and ƒeven inches diameter; the entire height of this piece is three feet.
        Fig. 5. Plate VII. repreƒents a ƒmall mortar, uƒed only for proving powder. We ƒhall give all the proportions of this piece, when we come to deƒcribe the manner of making that proof.
 

SECT. VII. Remark upon the Chambers of Mortars,

THE ƒpherical and pear-ƒhaped chambers are eƒteemed better for mortars than the cylindrical, not having the ƒame inconveniency as in cannon, becauƒe in mortars they are more eaƒily cleaned. Theƒe ƒort of mortars are alƒo more uƒed, at preƒent, than thoƒe with cylindrical chambers.
 

SECT. VIII. Of Bombs, and the Quantity of Powder with which they ought to be charged.

HITHERTO we have ƒpoken of the bomb only as a ƒort of bullet; it is now neceƒƒary to be more particular, that the reader may be more minutely acquainted with it.
        The figuresm and n (Plate VII., Fig. 3, 4.) may ƒerve for this purpoƒe. The firƒt m ƒhews a bomb as it appears to the eye, the ƒecond n repreƒents it in ƒection, or in profile, and confequently ƒhows its thickneƒs; the parts a and b of the bomb m are its handles, or the part by which it is lifted up; ƒ is the touch-hole, or aperture through which the powder is poured in to charge it.
        "Experience ƒhows (as M. Belidor tells us, in his Bombardier
François) that 15 pounds of powder ought to be put into a bomb of 12 inches, which weighs when charged about 145 pounds: that a bomb of 8 inches requires 4 pounds, weighing when charged about 40 pounds; that one of 6 inches requires 3 pounds, and weighs when charged a little more than 23 pounds: And, laƒtly, that 30 pounds of powder are required for a bomb of 17 inches 10 lines diameter, which weighs, when charged, about 520 pounds."
        But later experiments prove, that the ƒame bombs, charged with a much lets quantity of powder, will produce the ƒame effect. M. Belidor himƒelf has reduced this quantity to 2 pounds and an half, or 3 pounds for a bomb 12 inches, and one pound for a bomb of 8.
        It is evident that the deƒign of the powder, with which a bomb is charged, is to make it burƒt, and that if it burƒts with a quantity of powder leƒs than it is commonly charged with, that quantity is ƒufficient, and that all above it is abƒolutely loƒt.
        There is however one particular to be obƒerved, which is, that when bombs are intended to fire the buildings on which they are thrown, the larger the charge, the better they ƒucceed; but on all other occaƒions, the quantity of powder, more than ƒufficient to burƒt the bomb, cannot produce any advantageous effect.
        It appears by Figure n (Plate VII., Fig 4.): That the lower part of the bomb is thickeƒt, which is contriv'd that the bomb, being heavier on that ƒide, may be ƒure to fall upon it, and never upon the fuƒe c d, of which we ƒhall ƒpeak preƒently; this heavy under part is called the breech of the bomb. The diameter of a bomb ought at leaƒt to be 5 or 6 lines leƒs than the bore of the mortar, from which it is to be diƒcharged.
 

SECT. IX. Of the Fuƒes of Bombs.

THE fuƒe of the bomb is repreƒented by c d in Figure n (Plate VII.) It is a kind of little ƒruƒtum of a cone, concave within, made of linden, willow, or ƒome other very dry wood, filled with a compoƒition of the beƒt powder, ƒulphur and ƒalt-petre. The bomb being charged, this fuƒe is inƒerted in the cavity through the touch-hole, and when fired, communicates the fire to the powder with which the bomb is charged; the wood of the fuƒe, before it is charged, is called the Ampoulette.
        According to a regulation made in 1713, for ƒettling the proportion of the fuƒes to the bombs, thoƒe for bombs of 12 inches diameter ought to be 8 inches long, and 20 lines (or 12ths of an inch) diameter at the big end, 14 at the ƒmall, and 5 in their cavity or bore.
        The fuƒes for bombs are charged with great care, that nothing may prevent or ƒtop their communicating the fire to the powder in the centre of the bomb; they are driven and fixt into the bomb, ƒo that only about an inch and an half comes out beyond the touch-hole.
        Theƒe fuƒes are alƒo charged long before there is occaƒion to uƒe them; and that the compoƒition they are filled with may not fall out, or ƒpoil by growing damp or wet, the two ends are covered with a compoƒition of tallow, mixt either with bees-wax or pitch. When the fuƒe is to be put into the bomb, care is taken to open the little end, or cut it off; as to the great end, it is never opened till the bomb is in the mortar, and juƒt going to be fired.
 

SECT. X. Of the Inƒtruments neceƒƒary to charge Mortars, and of the manner of charging them.

TO charge a mortar (as in charging cannon) many inƒtruments are neceƒƒary.
        The principal are, a rammer of the ƒame diameter as the piece, to ram in and beat down the wadding and turf which cover the powder; an iron ƒcraper, to clean the bore and chamber of the mortar, and a little ƒpoon to clean more particularly the powder chamber; a wooden knife, of about a foot long, to force the earth cloƒe in round the ƒides of the bomb; there is need alƒo of priming-irons, aiming wedges, and two lint-flocks.
        The officer who directs the charging of the mortar, having aƒcertained the proper quantity of powder, cauƒes it to be put into the chamber of the mortar, and then to be covered with a wad, well beat down with the rammer. Over theƒe are put two or three ƒhovel-fuls of earth, which are alƒo well beat or rammed down; after which the bomb is placed upon this earth, as near the middle of the mortar as poƒƒible, with the fuƒe, or touch-hole, uppermoƒt; more earth is then put in, and preƒƒed down cloƒe all round the bomb, with the wooden knife juƒt mentioned, ƒo as to keep the bomb firm in the ƒituation it is placed in. All this being done, the officer points the mortar, that is, gives it the inclination neceƒƒary to carry the bomb to the place deƒign'd. When the mortar is thus fixed, the fuƒe is opened, the picker is alfo paƒƒed into the touch-hole of the mortar to clear it, and it is then primed with the fineƒt powder. This done, two ƒoldiers, taking each one of the lint-flocks, the firƒt lights the fuƒe, and the other fires the mortar. The bomb, thrown out by the explosion of the powder, is carried to the place intended, and the fuƒe, which ought to be exhauƒted at the moment of the bomb's falling, ƒets fire to the powder it is charged with; this, immediately, by its exploƒion, burƒts the bomb into ƒplinters, which are thrown off circularly round the point the bomb falls upon, and do conƒiderable damage on every ƒide.
 

SECT. XI. Remark.

IF the fuƒe ƒets fire to the bomb before it falls on the place intended, the bomb will burƒt in the air, and may do as much miƒchief among thoƒe who fired the mortar, as thoƒe againƒt whom it was diƒcharged. To prevent this inconveniency, it is ƒo contrived, that the fuƒe (the time of its burning out being pretty exactly known) ƒhall not fire the bomb till the moment of its fall on the place againƒt which it is thrown. To effect this (as the fuƒe will laƒt at leaƒt as long as the time the bomb is in going its greateƒt poƒƒible range) when a bomb is thrown to a great diƒtance, the fuƒe and the mortars are fired at the ƒame time, and when the bomb has not far to go, part of the fuƒe is ƒuffered to burn out before the mortar is diƒcharged.
 

SECT. XII. Of the manner of levelling, or pointing a Mortar, or giving it a proper degree of Inclination.

WE ƒhall now treat of the pointing a mortar, the method of which is as follows.
        Let a (Plate VIII) be a mortar mounted on its carriage, which is to be levelled, ƒo as to make (for inƒtance) an angle of 50 degrees with the horizon. A quadrant c d(4), divided into degrees, is placed on the mouth of the mortar, in ƒuch manner as that the ƒide of the quadrant c f ƒhall be parallel to the bore of the piece. At the centre of this quadrant f a thread is faƒtened, at the end of which hangs a plummit g; the mortar is to be raiƒed till this thread f g falls upon the 50th degree of the quadrant, counting from the point d, and then the mortar will make an angle of 50 degrees with the horizon; any other inclination may be given by the ƒame means at pleaƒure.
        It is evident that the arch d g is the meaƒure of the inclination of the mortar; for if the mortar were parallel to the horizon, the thread f g would fall upon the ƒide of the quadrant f d; now in proportion as the mortar is raiƒed, the thread will deƒcend towards c; therefore, &c.
 

SECT. XIII. Of Bombs fired by way of the Ricochet.

IN treating on the firing of cannon, we obƒerved, that Monƒ. the marƒhal de Vauban was the contriver of the ricochet, an invention which may be ƒaid to render the defences of the enemy uƒeleƒs, and which has brought the attack of places to great perfection. But this has been almoƒt wholly confined to cannon, unleƒs the name ricochet be allowed to the bombs thrown with the obus or hawitzer, (a kind of mortar which will be treated of in its place) which ƒtrictly correƒponds in effect with the ricochet, ƒince the uƒe of them is to roll in ƒhells among bodies of men, and there do great execution. But they do not appear to have been hitherto uƒed in the attack of places; the governors of the ƒchool of artillery at Strasburg, judging however that bombs fired by way of ricochet might be uƒed againƒt fortifications with great advantage, made ƒeveral experiments on the ƒubject in 1723, which are related by M. Belidor in his Bombardier François, from which the following account is extracted.
        "To fire bombs in ricochet, mortars of 8 inches diameter are made uƒe of, mounted upon cannon carriages. The batteries erected for this purpoƒe are placed upon the continuation of the branches of the covered way, becauƒe bombs there do ƒo great execution, that it is ƒcarce poƒƒible the troops ƒhould keep poƒƒeƒion of it. They break paliƒadoes, barrs, and intrenchments, which are made in the rentrant or entering place of arms, and create much more diƒorder than bullets; for they are not only bigger and heavier, but, after making many bounds, burƒt where they ƒtop, without entering the ground, and their ƒplinters are always fatal. Beƒides, theƒe mortars may be uƒed with greater expedition than cannon; for there is nothing to do, but to put the powder into the chamber, the bomb upon it, and fire; and as this may be done in 3 or 4 minutes, a battery of two mortars, uƒed in this manner, will throw thirty, or forty, bombs in an hour. I leave any one to judge (adds M. Belidor) if a covered way was flanked by ƒuch batteries, what garriƒon could maintain their ground, what advantage the beƒiegers would there have, in making a vigorous attack, and with how much facility they might advance their works.
        "As the bombs muƒt be prevented from entering the ground when they fall, becauƒe they would not then roll or bound, the mortars ought never to be pointed above 12 degrees; but any angle may be taken between 8 and 12, which is found moƒt convenient, with reƒpect to the charge the mortar is fired with, and the diƒtance of the place where the bomb is intended to begin to bound. The experiments made at Strasburg may ƒerve as rules on this ƒubject, and are as follow.
        "A battery was erected 70 fathom from the ƒaillant angle of the covered way of the half moon of the polygon belonging to this ƒchool; a mortar, pointed at 9 degrees above the horizontal line, and charged with three quarters of a pound of powder, threw the bombs upon the glacis at 2, 4, 6, 8, fathom from the parapet of the covered way, where riƒing with a bound, they went forward, falling firƒt in the branch between the two traverƒes, and then in the rentrant place of arms againƒt a ƒmall intrenchment which had been thrown up there on this occaƒion.
        "The piece was afterwards pointed at 10 degrees, with the ƒame charge, and after 5 or 6 times firing in this manner, it was obƒerved that the bombs fell in the place of arms of the ƒaillant angle, and there riƒing with a bound, fell again, as in the former, in the branch between the two traverƒes, and then into the rentrant place of arms. The mortar was at laƒt pointed at 11 degrees, and ƒtill fired with the ƒame charge; after diƒcharging it 5 or 6 times, it was obƒerved that the bomb ƒtill fell in the branch between the two traverƒes, and riƒing,went from thence over the covered way. From all this it was concluded, that the moƒt advantageous manner of firing by way of ricochet is, when the mortar is ƒo levelled that the bombs may fall on the crown of the covered way, or the ƒaillant place of arms, by which means they never fail of producing confiderable effects.
        "In order to try if the fuƒe would not be extinguished, either by the fall of the bomb, or its rolling in the ricochet, ƒeveral were diƒcharged with the fuƒe lighted, all which ƒucceeded, the fuƒe burning till it was quite confirmed.["]