standard system. The different devices for attaching the ring are numerous, and are worthy of study, especially Numbers 18 on Plate I, which apparently never fails to take the grooves and never loses the ring, nor throws off fragments of iron from the base of the shell, faults to which most of the other varieties seem liable.
The fifth system takes the grooves by the expansion of a lead sabot. It seems to be confined to large calibers, 7 inches and 6.4 inches, except sample 28 on Plate I, which is a strange shell, apparently designed for a breech-loader. The lead sometimes remains upon the shell, but is very liable to strip.
The sixth system is that of mr. Whitworth, whose 12-pounder guns the rebels use considerably. Some of the projectiles are English and some of rebel manufacture. They have even tried to make shall by boring out a cavity in the bolt to the diameter of their usual fuse-hole (0.9 inches), as on sample 30, Plate I. This, however, does not contain a sufficiently large bursting charge to be of service.
The seventh system, which is in common use, is that of Mr. Hotchkiss. Many of these projectiles are evidently of our manufacture, bearing Mr. Hotchkiss' name and patent stamp. Others have no mark and are, without doubt, of rebel manufacture. I have such samples, for calibers 5.2 inches and 3.3 inches, as well as the one drawn (Numbers 32, sheet I), which is 3 inches. The one of 3.3 inches has a large wire wound round the middle and covered by the lead, which I have never seen in those supplied by Mr. Hotchkiss.
The eight system is in some doubt. The specimen (Numbers 33, Plate II) is one of Mr. Schenkl's old model 30-pounder projectiles, which may possibly have been received from our batteries and fired back. It, however, has the characteristic copper fuse plug of the rebels, and they evidently must have made a sabot for it, of what material is not known. Among the ammunition captured by the Eighteenth Corps near Fort Harrison were several samples of 100-pounder and 30-pounder projectiles, which I have issued for use to my batteries, and upon which I shall report hereafter.
The drawing on Plate II show the kinds of ammunition used by our forces during this campaign. Every effort has been made to arrive at a correct judgment of their several excellencies and defects, by requiring accurate reports upon each round fired, whenever possible. The results already arrived at may perhaps be modified by the future firing, and, therefore, they will not be reported at present.
Major Trumbull, in command of all the siege artillery on the Eighteenth Corps front until the springing of the mine, remained after that date in charge of all the siege artillery in front of Petersburg until September 1, when his health, already impaired by overexertion, gave way, and for a time I lost his efficient aid. Of late, however, he has somewhat improved, and is now in command of the artillery, heavy and light in the lines of City Point, where his experience has been of great value in organizing the defense. Major Brooker relieved Major Trumbull at Petersburg, but in about a week became so sick as to be unfit for duty; Lieutenant-Colonel White relieved him on September 10, and remained in command until September 28, when Major Brooker was sufficiently recovered to resume the command, which he has retained, Lieutenant-Colonel White resuming his own important duties on my staff. To these three officers my thanks are due for their laborious exertions and skillful administration of a peculiarly delicate and difficult command.