I40 OF G UN-METALT

of the fluid against the shot, act in the direction of the axis ;the thicknefles determined by the line R QN, maybe muchdiminished without any risque of bursting the gun. Thefollowing observations made on more than 100 guns thatwere rendered unserviceable by the shocks of the shot, maybe adduced in order to ascertain some limits for this pro-portion. These guns in respect to thickness of metal, wereof three kinds: the first were determined by a scale madefrom the diameter of the bore; the thickness at the breachwas one diameter; at the end of the first reinforce 44; atthe beginning of the second reinforce 44 ; at the end of thesecond reinforce 44; at the beginning of the chase 44 j andat the muzzle The guns of the second kind were inthe same proportion, but the scale formed from the diameterof the shot, so that they were not so thick as the first kind.The third kind was as the second, proportioned from thediameter of the shot from the breech to the first reinforce ;but, at the beginning of the chase was only 44 of the dia-meter, and at the muzzle The least thickness of theswell of metal at the muzzle was, including the ornaments, ~of its diameter in the three kinds of guns, It was ob-served ;

r. That in the guns of the first kind, a very violentshock caused neither crack nor bulge in whatsoeverpart it struck: the force and direction of the shockbeing gathered from the form and depth of the cavity.

2. That in the guns of the second kind, the shothaving struck violently between the half of the chaseand the muzzle, the metal bulged out; and at thesucceeding round, the muzzle dropped.

3. In the guns of the third kind, bulges and crackswere observed at about §■ of the length of the chafe ;and though the exterior of the muzzle did not appearthe least altered; yet, at the next violent shock itdropped.

92. From the preceding observations (86) it may heconcluded; that if the gun from A to G (PI. 3, Fig. 8)has its thicknesses AC, O D —44 ot the diameter of thebore, and BFzr T * 4 ; the right line D F, will express thethicknefles necessary to resist the forces that tend to burst thegun, viz. the action of the fluid at N, and every other pointof the length of the bore, and the most violent shocks frontthe shot; provided that the swell of metal H at the itiuv

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