_CHAMBERS._—In 1787 and 1789 experiments were made at Woolwich with an 8 inch mortar, with four shifting chambers, to ascertain which form gives the longest range. The chambers were all of the same capacity, viz. 63.7 cubic inches, and contained two pounds of powder. Their forms were: 1st. Common conical chamber with the circular bottom. 2d. The same reversed. 3d. The cylindric chamber with circular bottom. 4th. The spheric chamber. The ranges were the medium of 6 rounds; from them it appears, that when the spheric chamber is filled with powder, it has the advantage in point of range; but when smaller charges are used, its ranges are found to be shorter than those of other forms. The conical (No. 1.) chamber of the present establishment gives the longest range under other circumstances. _CHARGES._ _Charges for Field Guns._ lbs. 12 Prs. Medium and Heavy for Round Shot 4 ” ” ” ” ” ” Case ” 3½ 12 Prs. Light ” Round ” 3 ” ” ” ” Case ” 3 6 Prs. Desaguliers ” Round ” 2¼ ” ” ” ” Case ” 2 6 Prs. Medium ” Round ” 2 ” ” ” ” Case ” 6 Prs. Light ” Round ” 1½ ” ” ” ” Case ” 1¼ 3 Prs. Heavy ” Round ” 1 ” ” ” ” Case ” 3 Prs. Light ” Round ” 12 oz. The charge for battering guns is ⅓ the weight of the round shot, for round shot, and ¼ of it for case shot. The charge for carronades is usually ¹/₁₂ the weight of the shot. The highest is ⅛, and the lowest ¹/₁₆. By the experiments made at Woolwich in March 1801, it is recommended, that when cylinder powder is used on service, the charges of field ordnance with round shot, shall be reduced to the usual quantities for case shot. The same experiments recommend, that the thickness or length of the wood bottom be varied, in order to change the position of the shot, and thereby save the bore; and that the paper cap which is usually thrown away on service, shall be put over the shot before it is introduced into the piece. For charges for small arms see the word Cartridges. _Charges of French Guns in French Weights._ lbs. 24 Prs. 8 } Siege 16 Prs. 5½ } 12 Prs. 4 } 8 Prs. 2½ } Field { ¼ less for 4 Prs. 1½ } { Case Shot. _CHEVAUX DE FRIZE._—The _body_ or _beam_ of a chevaux de frize is generally made 9 feet long, and 6 inches square, and weighs 41 lbs. The _spears_ are 33 in number, weighing 2 lb. each, are 5 feet long, and 1¼ inches square. They are placed 9½ inches asunder. _COMPOSITION._—For the composition of fuzes, portfires, tubes, carcasses, see those words.