Those which throw heavy shells, for, if used to enfilade a work, the shells lodge and explode in the traverses, and render the guns more liable to be dismounted, and their detachments put _hors de combat_. 14. What determines the _nature_ of the ricochet? The angle of fall: it is _flattened_ when this angle does not exceed 6°, and _curvated_ when it is between 10° and 12°. In the first of these fires, the velocities are great, and in the second small. 15. What are the charges for a _flattened ricochet_ for siege guns at an angle of about 3°? See Table, page 58. 16. What are the charges for a _flattened ricochet_ for siege howitzers at an angle of about 3°? See Table, page 58. 17. What are the charges for a _curvated ricochet_ for a siege howitzer at an angle of about 10°? See Table, page 58. [Sidenote: 76]] CHARGES FOR A FLATTENED RICOCHET FOR SIEGE-GUNS. ========================================== DISTANCE. |ELEVATION.| CHARGE. ----------+----------+-------------------- 660 yards.| 2° 45' |1-12 weight of ball. 550 “ | 3° |1-15 “ “ 440 “ | 3° 15' |1-20 “ “ 330 “ | 3° 35' |1-30 “ “ ----------+----------+-------------------- CHARGES FOR A FLATTENED RICOCHET FOR SIEGE HOWITZERS. ========================================== DISTANCE. |ELEVATION.| CHARGE. ----------+----------+-------------------- 550 yards.| 1° 45' | 3 lbs. 440 “ | 2° 15' | 2 lbs. 3 oz. 330 “ | 2° 15' | 1 lb. 12 oz. 220 “ | 2° 45' | 1 lb. 2 oz. ----------+----------+-------------------- CHARGES FOR A CURVATED RICOCHET FOR SIEGE HOWITZERS. ================================================================ DISTANCE. |ELEVATION.| CHARGE. | REMARKS. ----------+----------+-----------+------------------------------ 550 yards.| 7° 30' |1 lb. 4 oz.| The height of the object above 440 “ | “ |1 lb. 1 oz.| the level of the battery being 330 “ | “ | 14 oz.| supposed to be 20 feet. 220 “ | “ | 10 oz.| ----------+----------+-----------+------------------------------ [Sidenote: 77]] PART VI. RECOIL. 1. What is meant by the _recoil_ of a piece of artillery? The retrograde motion impressed upon cannon by the discharge is termed the _recoil_. 2. What causes the recoil of a piece? The gas produced by the ignition of the charge in the bore, expanding with equal force in every direction, finds only two ways of escape (the muzzle and vent); the pressure upon these points will therefore cease, while it will be proportionally increased upon the parts directly opposite, that is, the breech and the lower part of the first reinforce, producing in the first case the recoil, and in the other, indirectly, the dipping of the muzzle. 3. How far does a gun usually recoil?