340 Mr. Mallet on the Physical Conditions 



ments in naval construction, as well as the necessities of coast attack, developed within the 

 last year or two, have forced attention to the necessity of providing our ships with guns, 

 that shall throw solid shot of the greatest possible weight, and with the highest velocities 

 and longest ranges. 



After lengthened experiments and niany difficulties, it had been found that shells, up to 

 10 inches diameter, could be thrown at nearly horizontal ranges, and at high velocities, from 

 shell guns. The success was pushed too far. It was said that the new method rendered 

 useless tjie older notions of throwing shells by vertical fire, and that mortars were no longer 

 needed. The result was, that when the hour of trial came, we possessed scarcely any 

 mortars, and no mortar vessels, and did not know how properly to construct either. 

 Experience, gathered when it had become too late to employ it, proved how widely we 

 had erred, in abandoning and underrating the ancient methods of bombardment. 



So far from being fitly abandoned, it soon became evident that the adoption, upon 

 a larger and more extended scale than had ever before been known, of the system of case- 

 mated fortifications, for coast line fortresses, on the part of the enemy, would compel us to 

 reinforce the ancient powers of vertical fire, by increase of range, velocity of descent, and 

 weight of shell, if we were to produce any effect in that way upon these formidable defences. 

 Upon examining into the comparative increase of efiect that might be expected from 

 increase of diameter of shells, above those ordinarily in use, I found, with some surprise, 

 that the military literature of Europe, so far as I had access to it, did not contain an 

 attempt even to ascertain this in a rigid manner. Tables, indeed, exist in foreign services 

 (imperfectly in ours) of the range, deviation, penetration, &c., of the three or foiur sizes of 

 shell, long in common use ; but it does not seem to have ever occurred to any military 

 author to discuss these into general laws with relation to the variable diameter of the shell; 

 or if, admitting their basis"to be too narrow for such a discussion, to determine, a priori, 

 the physical and dynamic laws which, applied to shells of difl^erent magnitudes, would 

 enable such a comparison of efl!ect to be made. 



Having proposed to Government, about the latter end of 1854, the construction of shells 

 and mortars of 36 inches diameter, for certain special services, I found it necessary to make 

 some such investigation, to compare the efiects of shells of 36 inches diameter, and of given 

 proportions, with the largest existing shells then in the British service, viz., 13 inches 

 diameter. 



The following is an abstract, — I make no apology for adding it to this Note, as forcibly 

 indicating the value of increased magnitude in hollow projectiles, and of vertical fire. 



Relative Powers of Shells, in proportion to their Dimensions. 

 In the attack of fortified places by bombardment, the efficiency of similar shells, thrown 

 with equal address, would seem to depend upon — 



