Mounting of Naval Ordnance, 149 



Dupin also, in his ^^ Force Navale tie la Grande Bre- 

 tag7ie/' discusses this question erroneously. He arrives at 

 the conclusion that the muzzle is thrown upwards when the 

 recoil is checked, unless the plane of the breeching, when 

 tight, passes through the common centre of gravity, G, of the 

 gun and carriage; most likely not knowing that he was 

 denying a notorious fact from an imperfect, and, no doubt, 

 hasty consideration of the subject. 



As this is a very interesting question in the service of 

 naval artillery, we shall here endeavour to clear it of the 

 obscurity with which it has generally been treated. 



Taking the preceding diagram, representing a sea-service 

 gun, on a carriage of the usual construction, when the ship 

 is upright, let G be the common centre of gravity of the 

 gun and carriage ; this point being a little in the rear of the 

 trunnions, and about the height of their axis. Through G, 

 draw the vertical line GW -, and from the centres K and L of 

 the axletrees, draw KM, and KN, perpendicular to GW, and 

 join KG and GL. Now we may conceive that there is a given 

 weight at G, supported by the two inflexible lines GK and 

 GL given in position, and hence the whole system is capable 

 of turning on the point K or L, according to the magnitude, 

 point of application, and direction of any force that may be 

 applied in a plane at right angles to the platform, and paral- 

 lel to the axis of the gun. For instance, the elastic force of 

 a given quantity of powder, taking place in the axis of the 

 piece, will have a tendency to make the system turn about 

 the point L, during the recoil ; this tendency being developed 

 in proportion to the height of the axis above the said point. 

 On the contrary, if a force in an opposite direction, and at the 

 same height, were applied, it would, in like manner, cause 

 the system to turn about the point K. But, from the prin- 

 ciples of mechanics, the stability of the gun and carriage, 

 with respect to the point L, is in proportion to the line LN ; 

 and the stability of the system, with respect to the point K, 

 is proportional to the line KM. Hence, as the line WG is 

 generally very much nearer to K, than to L, making KM 

 much less than LN, it follows, that it requires a proportion - 

 ably larger force to overcome the stability, with regard to 

 the point L, than the stability with regard to the point K *. 



♦ It is evident, from this step of the investigation, that if the carriage be much 

 shortened in the rear of the Une GW, the line LN may be so much diminished, 

 that the gun and carriage may be thrown backwards — a circumstance by no means 

 unfrequent, when it has been foolishly attempted to mount lighter and shorter 

 pieces of ordnance on short carriages of the same height. I or, with the same 

 charges of powder, the initial velocities suffer but a small decrease, and conse- 

 quently, the momentum of recoil is nearly the same as in the larger pieces . 



