334 Charges of greatest Efficacy for Artillery at Sea. 



of a very brittle nature, such as stone or brick, then that 

 charge is to be used which will give the greatest velocity to 

 the shot to produce the maximum effect. But in many cases 

 of bombardment this charge is by no means to be preferred; 

 for though the effect produced each individual time be 



freater, yet in any considerable time the whole effect would 

 e less than that from a smaller charge oftener fired, on ac- 

 count of the extreme heat it would give to the engine after 

 a few discharges; and in consequence of which greater time 

 would be required for cooling the gun and preparing it for 

 further service. 



Example II. 



Required the charge for a 24-pounder shot to burst open 

 the gates of a city with the greatest ease possible, they be- 

 ing o/'elm one foot thick. 



Here the object to be penetrated being elm, the small 



. , , c , Sdv*w f (& + ZD)dv*w\ 



letters in the general formula -=r ~— -[ = ----- --- _ . : 



6 2Ds x i ooo* v 2Ds x l600 a / 



must be made to denote the several numbers of some ex- 

 periment made in the penetration of this substance. Taking, 

 therefore, the experiment of Dr, Mutton contained in the 

 5th problem of his elegant Exercises on Forces, we have 



d— — ft. v = 1500, and S = — ft.; also by the question 



S = 1 ft. D = -46, and w = 24 lbs. therefore *^°?f!^ 

 1-23x1x1500^x24 830'25 „ ., t . 



= ^ — tS ~t, — ,>™« = txt^t = 4-33S6slbs. or 4lbs. 



2 X '46 x \ j X 16W IQI'36 

 S^ozs. nearly the weight of the charge required in this case. 

 Retaining the experiment of Dr. Hutton as a standard for 

 all cases where the substance to be penetrated is of elm, we 



shall have by reduction ^-^ ='06 7 6 x — £- - : 



the charge for any piece the diameter of whose shot is D, 



and weight w, S being the thickness of the object as be- 

 fore. 



It is not unworthy of remark, that the gates of a besieged 

 place, or any like things, might be effectually broken open 

 by the gun itself, charged only with powder; by placing it 

 close to the gates with its muzzle from them; the mo- 

 mentum of recoil being generally sufficient to force such 

 objects completely. 



LXII. Cases 



