The wisdom displayed in rifling barrels with the gathering or deepening groove may be doubted; it admits of serious consideration, whether or not it tends to increase the friction of the bullet passing outward. It is evident that did the bullet expand all at once it would do so; but as this is well known not to be the case, the question arises what is the advantage gained? for it is asserted on high authority that it improves the shooting. The mere deepening of the grooves at the breech end can have but little effect; and the question is, does the shallowing of the grooves as the bullet approaches the muzzle, produce the effect? We think it does. In the process of rifling these barrels, the rifling tool, by a very ingenious arrangement of screws, is caused gradually to cut deeper as it travels from the muzzle to the breech, so that when finished the depth of grooves at the muzzle is ·005 of an inch; half-way down the barrel it is ·010, and at the breech end ·015: thus gradually deepening 10/1000 of an inch, whereas the usual method of rifling is to have one uniform depth of ·010 inches. From the contraction of the protuberances on the bullet from 1/10 to 1/5000 of an inch in passing up the barrel, results the apparent benefit: such a reduction would surely allow of the bullet continuing its flight with less friction on the atmosphere; for it cannot be too often repeated that perfect smoothness, even to a polished surface, is essential to the easy passage of all bullets through the air. There are some rather curious deductions obtained by practice alone, which to ordinary minds appear of trifling importance; but they clearly show that correct rifle-shooting can only be obtained by the most perfect arrangement in the rifling and scientific construction of the barrels. The Government have lately adopted a highly finished and costly rifle arm, with sword bayonet attached to the usual form of bar soldered to the end of the barrels on the right side. When these barrels were first constructed, they were made lighter than experience subsequently showed they ought to be; for it was found that the barrel not expanding equally with the other portions at this necessarily rigid point, influenced the shooting of the gun to a considerable extent; so that an increase of metal was found necessary. The difficulty of obtaining good shooting with double rifles, one side of each barrel being held rigid whilst the other is yielding, explains the difficulty, and points to the remedy: an increase of metal, or, what would be more convenient, the adoption of the most perfect laminated steel for all double rifles; it being self-evident that soft barrels and correct rifle-shooting are to a certain extent incompatible.