Charges of greatest Efficacy for Artillery at Sea. 325 



applicable to the land service, arranged upon the plan of Sir 

 Home Popham's tor the naval service, will be necessary. 



When a tent or any other object is fixed upon as a cen- 

 tre-point, it is then generally unnecessary to use the double 

 ball. 



When stations are taken below the horizon, the white 

 sides of the balls are to be turned to your correspondent, 

 and it is advantageous to have the men in white cr fatigue 

 dresses. 



When stations are taken above the horizon, the black 

 sides are to be turned towards your correspondent, and then 

 it is advantageous to have the men in uniform. 

 I am, sir, 



Your obedient servant, 



Surry Institution, KNIGHT SpENCER. 

 Nov. 6, 1810. 

 x..: 7 ..':,-, • ■ ■ ' ■ ' ■ '■ . ' : ' ' : < ■ r 



LXI. On the Penetration of Balls into uniform resisting 

 Substances. By W. Moore, Esq. 



To Mr. Tilloch. 



Sir, Ohould the following paper on the destruction of 

 an enemy's vessel at sea by artillery be thought deserving 

 a place in your excellent Magazine, you are at liberty to 

 make use of it accordingly. 

 I am, sir, 



Your most obedient servant, 



Royal Military Academy, W # MOORE. 



Woolwich, November 10, 1810. 



Lemma I. 



If two spheres of different diameters and different specific 

 gravities impinge perpendicularly on two uniform resisting 

 fixed obstacles, and penetrate into them ; the forces which 

 retard the progress of the spheres will be as the absolute re- 

 sisting forces or strengths of the fibres of the substances 

 directly, and the diameters and specific gravities of the 

 sp h eres i n ' crse ly . 



Lei R and r denote the absolute resisting forces of the 

 two substances ; F and/ the retardive forces ; D, d the dia- 

 meters of the spheres; O, q their quantities of matter, 

 and N, n their respective specific quantities. Then the 

 whole resistances to the spheres, being bv mechanics pro- 

 portional to the quantities of motion destroyed in a given 

 time, will be as the absolute resisting forces of the sub- 



X 3j§ stances 



