a 10-pounder rifle projectile at 600 yards range upon a rope mantlet, made at Fort Monroe, and only about four inches thick. The shot was deflected, breaking the lashing of the mantlet and throwing down the pole supports, but was so much checked in velocity by so doing as to then knock a man down, without seriously injuring him. In other cases these thin mantles have been penetrated even by musket-balls, where the ropes were not closely lashed together, but the experience of the campaign has convinced me that a thickness of four and five-tenths inches is, all things considered the best which can be given them. In this connection, it may be well to call attention to the fact that we have had great difficulty in drawing heavy guns and supplies through the covered ways leading to Fort Sedgwick, owing to the sharp curves at the angles. In such places security must in part be sacrificed to facility have been more than once dismounted in turning these corners. As most of the magazines have been made under the superintendence of my officers, it may be well to state that the plan adopted, putting them in secure positions and making the chambers entirely below ground, roofed by heavy logs, and covered by dirt some six feet thick, has been found to be both simple and safe. Boards have seldom been used either for the side or the floor, which is made to drain into a barrel near the entrance. The usual dimensions, in the clear, have been six feet wide by five feet deep, length to vary according to capacity required. In no instance has one of them blown up, although often hit by the rebel projectiles; and even in heavy rains, such as that of August 15, at Petersburg, when several soldiers in the low bottom were washed away and drowned, no loss of ammunition, except in one battery, has occurred from leakage.

The large amount of mortar firing during this campaign has disclosed one defect which should be corrected. The friction primers are driven out of the vent with great violence by the explosion and occasions serious danger to the cannoneers. One valuable officer of my regiment, Lieutenant Andrews, lost the sight of one of his eyes from this cause; another, Lieutenant Jackson, had a narrow escape, being severely cut on the forehead, while the instances of injury more or less serious to enlisted men will, I think, fully amount to a dozen. The vents should be covered by a cap similar to that used for the Whitworth gun, and the line of metal should be permanently and accurately marked on all mortars. Moreover, what is not the case now, some convenient hook should be arranged for guiding the lanyard in a direction perpendicular to the vent. In other respects I regard the new mortars and carriages as vast improvements on the old models; in fact, as perfect. Several precautions to insure rapidity and precision of mortar fire have been suggested by the intelligent observation of Captain Osborne, Lieutenant Jackson, and other officers commanding batteries. Thus a wooden-handled steel scraper, made in the shape of a hoe, with a double edge, curvature 6.5 inches, was found to reduce more than one-half the time required to serve the 13-inch mortar. Although the fuses for this mortar were old and poor they were made to almost invariably burn by driving them gently, so as not to shake out the composition, and by placing a train of dry powder from the top of the shell to the fuse, and another where the fuse would strike the bottom of the bore in rolling out, both made to remain in place by wetting the iron. It was also found that wooden fuses should not be sunned, the powder should be well stirred in the barrel before firing, and that in inserting the Coehorn shell its paper fuse should be placed near to the top of the bore to insure its