The weight of a hollow 13-inch shell is 190 lbs.; the bursting powder 6 lbs. 8 oz.; the weight, if cast solid, would be 290 lbs.: thus the action of so large a body on the atmosphere must be immense of itself. There seems to be much difficulty in projecting masses of great diameter, from this cause; and this should lead us to seek, as indeed it points to, another material for fabricating projectiles. As weight is less in substance, and, of course, less in space, much less resistance, in proportion, will exist in a bore of six inches than in one of twelve; and a greater projectile force will be generated with fewer countervailing disadvantages. The first step in the vast improvements about to be effected in gunnery, has been successfully taken by Mr. Monk, of Woolwich arsenal, who has induced the authorities to allow a gun to be made from drawings and calculations of his own. The dimensions of the gun are as follows: length from cascable to muzzle, 11 feet; weight, 97 cwt. 3 qrs.; bore, 7-7/10 inches; weight of solid shot, 55 lbs.; shell, 42 lbs.; windage, 0·175; charge, 16 lbs. of powder; giving a range, at 32° of elevation, of 5,327 yards. _A compound shot_, (a shell filled with lead), was projected 5,720 yards, or _three miles and a quarter_, at a velocity, during the first second of time, of 2,400 feet per second, and occupying during the whole flight only 29-1/2 seconds. The comparative weight of gun and shot is 1 to 220. A course of experiments, extending over seventeen years, has firmly established this gun as the best ever yet constructed. Many attempts have been made to excel it, but all have failed. Guns have been made on drawings varying not more than three-tenths of an inch in their dimensions from those of his gun, and, with extreme _modesty_, the individuals have claimed a right to compete with Mr. Monk; and have even obtained competing trials, without any claim whatever to the discovery of the principle of it; coming into competition by no just claim or merit, but solely from the tendency to supersede any improvement emanating from a _civilian_. Eighteen, twenty-four, and thirty-two pounders are now, however, constructed on this model;--indeed the improvement is so great and so apparent, as to overcome every obstacle as yet thrown in its way. With no wish to detract from the merit of Mr. Monk’s invention (upon which I congratulate him and the country) but, in justice to myself, I may remind some of my readers, that in “The Gun,” published early in 1835, I clearly laid down the principle in _projectile force_, on which this gun is constructed; and as he has since so successfully accomplished this great improvement, he must permit me to say, that the principle is the same which I have striven for, for many years.