The manufacture of these guns was originally in the hands of the inventors, and it is quite evident that they must have taken great pains with the form of the gun, and also have taken special care that the material of which it was constructed was of the very best quality. There is too much reason to doubt the proficiency of military men in the science of metallurgy; and the British system of depending solely on their knowledge for the last half century, has no doubt proved an obstacle to advancement in the science of gunnery. [Illustration: Monck’s 56-pounder gun.] The gun which ranks next is Monck’s 56-pounder. Although not a chambered gun, it will be seen, from the diagram (see p. 117), to be an attempt (if not a perfectly successful one) to obtain uniformity of thickness in every part of the arc. The durability of these guns ranks as we have placed them. The next in rotation is the 8-inch or 68-pounder (see p. 114); which, although not the original sized gun that was rifled for the Lancaster shell, yet it was the one eventually used for that projectile up to the end of its very brief career. [Illustration: 10-inch or 86-pounder gun.] The 10-inch gun of 95 cwt., delineated at page 117, will be seen to be defective in its outlines when tested by the principles before laid down, and the fact of more 10-inch guns bursting at Sebastopol than any others (mortars only excepted), may be taken as exclusive evidence of its imperfection. The bursting of mortars is quite notorious, especially the 13-inch mortars used for sea-service in the attack on Sweaborg. A slight examination of the engraving of one will be sufficient to convince any person that, if what has already been advanced on the form of guns can lay claim to being scientific, then this is of all guns the most unscientific that was ever manufactured. Its durability, too, like its shape, is of a very low order. [Illustration: 13-inch sea-service mortar.] The 13-inch land mortar depicted below is a much more serviceable production, because it contains much less metal. [Illustration: 13-inch land-service mortar.] Mortars will retain their place in spite of all improvements. Rifling is inapplicable to them. Their principal utility consists in obtaining a vertical fire; the shell being pitched to a great height, so as to fall into places that cannot be assailed by a horizontal fire.