4# the properties

might be adduced in support of this, but the common sky*socket fully exemplifies it.

97. When lire is introduced into the vent of a gun, theSction of the breech against the coins is in proportion to thedensity of the elastic fluid in the charging cylinder: now asthe wad and shot cannot move before there be a sufficientquantity of the fluid generated to overcome their resistance,and force out the column of air from the bore of the gun ;if the wad be too strongly rammed, or a part only of thepowder take fire, or more than one shot be put into the.gun, or it be more elevated at one discharge than another, theresistance to the fluid being increased by one or more of thesecauses, a greater quantity must be generated before the shotand wad will be moved. Before this motion commences,there can be no recoil (95), for the shot and wad form, asit were, a part of the gun itself: wherefore, if so large aquantity of substances be put into a gun, as totally to pre-vent, by their resistance, the escape of the elastic fluid, therewill be no other movement in the piece than that of thebreech up and.down against the coins ; which might, if ne-cessary, be more fully demonstrated. Moreover, since apart Of the elastic fluid escapes through the vent during thetime of its generation in the charging cylinder, it is clear,that the action of the breech against the coins in the oppo-site direction, must commence , as soon as the powder takesfire, but the recoil will begin sooner or later according to theresistance opposed to the explosion.

98* Hence, if the movement of the breech up and downhas not totally ceased before the (hot quits the gun, it maybe thrown above or below the point aimed at. When thewheels are of unequal diameters, or not placed in the inter-vals of the corresponding lines and nails, or the platform onwhich the gun moves while the shot is passing along thebore, is not even and solid ; in all these cases, the gun will notrecoil in the proper direction, and the shot will be thrownWide of the mark.

. 99. The length of the recoil during the time that theshot is passing along the bore varies according to circum-stances, If the charge, for instance, be rammed in the com-mon, method* and the gun placed on an even horizontalplatform, the elastic fluid must exert more force to move thecharge than to move the gun ; as is the cafe in using the wad-hook to draw. out the charge, the gun being drawn forward

before