280 Charges of greatest Efficacy for Artillery at Sea. 
been determined from experiment that a charge of half a 
pound impelled a shot weighing one pound with a velo- 
city of 1600 feet per second : we shall, considering V the 
velocity of any ball impinging on the side of the vessel, 
have for the expression of the charge impelling it through 
8 dnHv 2 w 
the space x 
Now to apply this in the present instance, it is first 
necessary that a case be known concerning the penetra- 
tion of a given shot into oak. Such a case is presented at 
page 273 of Dr. Hutton’s Robins’s New Principles of 
Gunnery. It is there asserted that an 18-pounder cast- 
iron ball penetrated a block of well-seasoned oak, such 
as ships of war are generally built with, to the depth of 
3? inches when fired with a velocity of 400 feet per se- 
cond. Making, therefore, this the standard of compari- 
son for all cases where the object is of oak substance, we 
400 2 x *42 
shall have for the charge generally — x 
& 2 x 16OO 2 x|- 
" D ~ N ; or, because the balls are of the same specific 
gravity, and the substance the same, or R “ r*, and N — n; 
400 2 x -42 S w S w 
it will be 7- X ~045 x that is the 
2 x 1600 2 x _L D D 
24 
charge varies as the space to be penetrated and weight 
of ball directly, and diameter of the ball inversely. 
Rut the charge by the question being to produce the 
greatest effect possible in the destruction of the vessel ; 
8 in the above formula must always be put equal to the 
given thickness of its side plus the radius of the hall 5 
since it is well ascertained that, for a shot to produce the 
most damage to any splintering object, such as oak ; it 
must lose all its motion just as it quits the superior or 
further surface of it. Hence the charge in question is 
