ignition. We may derive some useful hints from the rebel smooth-bore ammunition. Thus, their Coehorn shells are provided with ears, which is a great improvement over our system of banding. The interior surface of some of their 12-pounder shells are regular dodecahedrons; of others it consists of an upper and lower pentagon connected by ten equal trapezoids. The effect of both these devices is to cause the shell on bursting to divide into twelve pieces, weighing about a pound each, and thus to secure the maximum effect. It is a decided success, the former shape appearing to be more uniformly successful than the latter. Their system of filling spherical case with iron balls is a failure, the weight not being sufficient to render them effective.
The great problem, what is practically the best projectile for rifled artillery, has been carefully investigated during this campaign, both by requiring full reports of our own firing and by carefully collecting all varieties of projectiles fired by the rebels in return. Drawings of this collection and of our own projectiles have been kindly photographed for me by Major Michler, chief engineer, Army of the Potomac, and copies of the two sheets are appended.* The collection itself has been sent to the military museum at West Point. The following facts as to the rebel projectiles are worthy of notice. Their variety is very great, forty-five kinds being shown in the photograph, while three more have been since secured. They may, however, be classified into eight systems, according to the devices for making them take the grooves.
The first device is a cupped copper place, secured to the shell by a screw, and held firm by radial grooves, generally seven in number, but sometimes six. One sample bears Brooke's name upon the cup. It seems to be confined to the heavier guns exclusively, samples of the calibers, 7 inches, 6.4 inches, and 4.2 inches, alone being collected.. The projectiles appear to take the grooves well, but their plates are often missing, showing that it would be dangerous to use them over troops.
The second device consists of making the projectiles of wrought-iron, the bottom cupped like a lead bullet. This is rare, only two calibers (7-inches and 4.62 inches) being collected. It seems to be faulty only from its expense. Both samples were solid shot, apparently designed for firing at iron-clad vessels.
The third device is a curved copper place, secured by a screw and held firm by three dowels, made sometimes of three copper projections from the plate, extending into holes in the iron base of the shell, and sometimes of three iron projections from the base of the shell, extending through holes in the plate. The explosion of the powder flattens the place, and thus gives the rifled motion by increasing its caliber. This system is liable to the objection that the plate almost invariably separates from the shell, rendering the projectile unfit to be used over troops. It is, however, quite common, samples of the following calibers having been collected, 7 inches, 6.4 inches, 4.62 inches, and 2.2 inches. It is even used to render serviceable projectiles made upon other systems which are failures, as in Nos. 37 and 38, Plate II.
The fourth system is that of Read, which closely resembles Parrott's. This is very common, no less than twenty different kinds of projectiles being collected; seven have wrought-iron cups, calibers 6.4 inches, 4.2 inches, 3.67 inches, and 3 inches; eleven have copper rings, calibers 8 inches, 7 inches, 4.62 inches, 4.2 inches, 3.67 inches, and 3 inches. The larger samples are rare, but for field guns this seems to be the
*To appear in the Atlas.