Curmlineal Sterns of Ships. 205 



stances, be made to " cross," and consequently, that a *^ •point of 

 impunity" necessarily existed. 



Desirous however of discovering, if it would be possible under 

 any circumstances, consistently with the preservation of the frame 

 of the ship, to make the lines of fire issuing from the last-mentioned 

 ports intersect eacli other, an estimate was made, to determine 

 what alteration would be produced in the bearing of the gun, at the 

 stern-port, by supposing the rudder-head to be removed ; since 

 such an alteration, would necessarily have the effect of changing 

 the direction of the line of fire C c, by causing it to approximate 

 in some degree to the direction B h. The utmost difference, how- 

 ever, that could be produced by this arrangement, in the bearing of 

 the gun, amounted only to a diminution of a degree and a half of 

 the divergence before determined ; the new line of fire being in the 

 direction E e, and which therefore still kept the bearings of the two 

 guns from a state of parallelism, and consequently preserved a 

 " point of impunity" between them. 



The undefended arc h c, was of course diminished, by the same 

 quantity, as the divergence of the stern-gun was altered, the arc be 

 amounting in this new condition to thirty-one degrees. Hence it 

 appears, that the lines of fire proceeding from the after broadside- 

 port, and the adjacent port in the stern, cannot be made to cross, 

 even when the rudder-head is removed, unless by destroying one of 

 tlie sides of the former port, or a part of the stern-frame ; and that 

 a point of impunity therefore exists, on the quarter of a square 

 stern,* which it is impossible altogether to remove, unless by 



* It may perhaps be urged against this train of observation, that a point of 

 impunity can scarcely be said to exist practically, when the divergence of the 

 lines of fire is so small, and their distance, at their origin, so inconsiderable. 

 But, it should be remembered, thai in these experiments the utmost limit was 

 given to the bearings of the guns ; and that to obtain the extreme lines of fire 

 above alluded to, much more time and labour was consumed, than could rea- 

 sonably be afforded in the day of balllc ; and that therefore the divergence of 

 the lines of fire from each other may be fairly considered, in a practical point of 

 view, to be tfrcaler liij manij dcfjrees than the quantity above determined ; and 

 conse<iuently that the existence of the point of iinjninily will be rendered propor- 



