in the military art, a short piece of ordnance, thick and wide, proper for throwing bombs, carcases, shells, stones, bags filled with grape-shot, &c. See GUNNERY, No. 50.

Land Mortars, are those used in sieges, and of late in battles, mounted on beds made of solid timber, consisting generally of four pieces, those of the royal and cohorn excepted, which are but one single block; and both mortar and bed are transported on block-carriages. There is likewise a kind of land mortars, mounted on travelling carriages, invented by Count Buckeburg, which may be elevated to any degree; whereas ours are fixed to an angle of 45 degrees, and firmly lashed with ropes. The following table shows the weight of land mortars and shells; together with the quantity of powder the chambers hold when full; the weight of the shells, and powder for loading them.

| Diameter of mortars | 13-inch | 10-inch | 8-inch | 5.8-inch royal | 4.6-inch cohorn | |---------------------|---------|---------|--------|---------------|----------------| | Mortar's weight | C. qr. lb. | C. qr. lb. | C. qr. lb. | C. qr. lb. | C. qr. lb. | | Shell's weight | 25 0 10 | 2 18 4 | 0 20 1 | 1 0 3 | | Shell's cont. of powder | 1 2 15 0 | 2 25 0 | 1 15 0 | 0 12 0 | 7 | | Chamber's cont. of powder | 9 4 8 | 4 14 12 | 2 3 8 | 1 1 8 | 8 |

Sea Mortars, are those which are fixed in bomb vessels for bombarding places by sea: and as they are generally fired at a much greater distance than that which is required by land, they are made somewhat longer and much heavier than the land mortars. The following table exhibits the weight of the sea mortars and shells, and also of their full charges.

| Nature of the mortar | Powder contained in the chamber when full | Weight of the mortar | Weight of the shell when fixed | Weight of powder contained in the shell | |----------------------|------------------------------------------|---------------------|-------------------------------|----------------------------------------| | 10-inch howitzer | lb. oz. | C. qr. lb. | lb. | lb. oz. | | 13-inch mortar | 12 0 | 31 2 26 | 198 | 7 0 | | 10-inch mortar | 30 0 | 81 2 1 | 93 |

To Charge or Load a Mortar, the proper quantity of gunpowder is put into the chamber, and if there be any vacant space they fill it up with hay; some choose a wooden plug: over this they lay a turf, some a wooden tampion fitted to the bore of the piece; and lastly the bomb; taking care that the fuse be in the axis thereof, and the orifice be turned from the muzzle of the piece: what space remains is to be filled up with hay, straw, turf, &c. so as the load may not be exploded without the utmost violence. The quantity of gunpowder to be used is found by dividing the weight of the bomb by 30; though this rule is not always to be strictly observed.

When the proper quantity of powder necessary to charge a sea mortar is put into the chamber, it is covered with a wad well beat down with the rammer. After this the fixed shell is placed upon the wad, as near the middle of the mortar as possible, with the fuse hole uppermost, and another wad pressed down close upon it, so as to keep the shell firm in its position. The officer then points the mortar according to the proposed inclination.—When the mortar is thus fixed, the fuse is opened; the priming iron is also thrust into the touch-hole of the mortar to clear it, after which it is primed with the finest powder. This done, two of the matroos or sailors, taking each one of the matches, the first lights the fuse, and the other fires the mortar. The bomb, thrown out by the explosion of the powder, is carried to the place intended: and the fuse, which ought to be exhausted at the instant of the shell's falling, inflames the powder contained in it, and bursts the shell in splinters; which, flying off circularly, occasion incredible mischief wherever they reach.

If the service of mortars should render it necessary to use pound shots, 200 of them with a wooden bottom are to be put into the 13 inch mortar, and a quantity of powder not exceeding 5 pounds; and 100 of the above shot with 2½ pounds of powder, for the 10 inch mortar, or three pounds at most.

To Elevate the Mortar so as its axis may make any given angle with the horizon, they apply the artillery level or gunner's quadrant. An elevation of 70 or 80 degrees is what is commonly chosen for rendering mortars most serviceable in calling shells into towns, forts, &c., though the greatest range be at 45 degrees.

All the English mortars are fixed to an angle of 45 degrees, and lashed strongly with ropes at that elevation. Although in a siege there is only one case in which shells should be thrown with an angle of 45 degrees; that is, when the battery is so far off that they cannot otherwise reach the works; for when shells are thrown out of the trenches into the works of a fortification, or from the town into the trenches, they should have as little elevation as possible, in order to roll along, and not bury themselves; whereby the damage they do, and the terror they occasion, are much greater than if they sink into the ground. On the contrary, when shells are thrown upon magazines or any other buildings, with an intention to destroy them, the mortars should be elevated as high as possible, that the shells may acquire a greater force in their fall, and consequently do greater execution.

If all mortar pieces were, as they ought to be, exactly similar, and their requisites of powder as the cubes of the diameters of their several bores, and if their shells, bombs, carcasses, &c., were also similar; then, comparing like with like, their ranges on the plane of the horizon, under the same degree of elevation, would be equal; and consequently one piece being well proved, i.e., the range of the grenade, bomb, carcass, &c., being found to any degree of elevation, the whole work of the mortar piece would become very easy and exact.

But since mortars are not thus similar, it is required, that the range of the piece, at some known degree of elevation, be accurately found by measuring; and from hence all the other ranges may be determined.

Thus, to find the range of the piece at any other elevation required; say, As the fine of double the angle under which the experiment was made, is to the fine of double the angle proposed, so is the range known to the range required.

Suppose, for instance, it be found, that the range of a piece, elevated to 30°, is 2000 yards; to find the range of the same piece with the same charge when elevated to 45°; take the fine of 60°, the double of 30°, and make it the first term of the rule of three; the second term must be the fine of 90°, the double of 45°, and the third the given range 2000; the fourth term will be 2310, the range of the piece at 45°. If the elevation be greater than 45°, instead of doubling it, take the fine of double its complement to 90°. As suppose the elevation of a piece be 50°, take the fine of 80°, the double of 40°. Again, if a determinate distance to which a shot is to be cast, be given, and the angle of elevation to produce that effect be required; the range known must be the first term in the rule of three, which suppose 2000 yards; the range proposed, which we suppose 1600 yards, the second term; and the fine of 60° double of the elevation for the range of 2000 yards, the third term. The fourth term will be found the fine of 43° 52', whose half 21° 56' is the angle of elevation the piece must have to produce the desired effect. And if 21° 56' be taken from 90°, you will have 68° 4' for the other elevation of the piece, with which the same effect will likewise be produced.

Note. To avoid the trouble of finding fines of double the angles of the proposed elevations, Galileo and Torricelli give us the following table, wherein the fines of the angles fought are had by inspection.

| Degrees | Degrees | Ranges | Degrees | Degrees | Ranges | |---------|---------|--------|---------|---------|--------| | 90 | 0 | 0 | 0 | 0 | 0 | | 89 | 1 | 349 | 66 | 24 | 7431 | | 88 | 2 | 698 | 65 | 25 | 7660 | | 87 | 3 | 1045 | 64 | 26 | 7880 | | 86 | 4 | 1392 | 63 | 27 | 8090 | | 85 | 5 | 1736 | 62 | 28 | 8290 | | 84 | 6 | 2709 | 61 | 29 | 8480 | | 83 | 7 | 2419 | 60 | 30 | 8660 | | 82 | 8 | 2536 | 59 | 31 | 8829 | | 81 | 9 | 3092 | 58 | 32 | 8988 | | 80 | 10 | 3420 | 57 | 33 | 9135 | | 79 | 11 | 3746 | 56 | 34 | 9272 | | 78 | 12 | 4067 | 55 | 35 | 9397 | | 77 | 13 | 4384 | 54 | 36 | 9511 | | 76 | 14 | 4695 | 53 | 37 | 9613 | | 75 | 15 | 5000 | 52 | 38 | 9723 | | 74 | 16 | 5299 | 51 | 39 | 9731 | | 73 | 17 | 5592 | 50 | 40 | 9841 | | 72 | 18 | 5870 | 49 | 41 | 9993 | | 71 | 19 | 6157 | 48 | 42 | 9945 | | 70 | 20 | 6428 | 47 | 43 | 9976 | | 69 | 21 | 6691 | 46 | 44 | 9994 | | 68 | 22 | 6947 | 45 | 45 | 10000 | | 67 | 23 | 7193 | | | | MOR

The use of the table is obvious. Suppose, for instance, it be known by experiment, that a mortar elevated 15° charged with three pounds of powder, will throw a bomb to the distance of 350 fathoms; and it be required, with the same charge, to throw a bomb 100 fathoms farther; seek in the table the number answering to 15 degrees, and you will find it 5000. Then as 350 is to 450, so is 5000 to a fourth number, which is 6428. Find this number, or the nearest to it, in the table, and against it you will find 20° or 70°; the proper angles of elevation.