ENGINEER DEPARTMENT, November 18, 1864.

CHARLES A. DANA, Esq.,

Assistant Secretary of War:

SIR: Please find herewith my views on the subject of destroying Fort Caswell by exploding a vessel loaded with gunpowder at the nearest point she could approach that work, and in reply to your desire to be furnished with such information.

On the destruction of Fort Caswell and Fort Fisher, and their capture, by an explosion of gunpowder.

FORT CASWELL.

It is proposed and considered practicable to destroy Fort Caswell, or its garrison, by blowing up a large ship loaded with gunpowder. This ship is to be conducted to the nearest point to the fort accessible to a vessel of her draught of water, and there exploded by some fuse or match under control of the parties navigating the vessel to her destination. The expectation and reliance is upon destroying this fort or its garrison by the effects of the blast of an immense quantity of powder, not less than 560,000 pounds, some of which it is proposed to take from damaged supplies now on hand. Such I understand to be the project on which my opinion is desired by the War Department.

Is this scheme practicable and likely to be attended with favorable results? Does it promise such reasonable results as to justify the consumption of so large an amount of our military supplies?

On examining the plans and hydrography about this work and its approaches from the sea, it appears that no vessel drawing ten feet of water can approach nearer to the fort than 450 yards; to reach which point she must make a circuitous course, exposed to the batteries of the fort. If served with hot shot and shell there is reason to believe she must be set on fire before she can reach the destined position. She may be sunk in attempting to reach her destination, and is liable to self-destruction by the powder being exploded by direct shot or shells from the batteries, or by fire caused by hot shot and shell. Should these projectiles strike and penetrate a wooden vessel conflagration must follow. It is very doubtful whether men would go on board such a burning ship, so loaded with powder, to extinguish the flame; and if they did so, whether it could be subdued in parts of the ship through which a hot shot might pass and ignite the woodwork, tar, and oakum exposed to such projectiles. Under such circumstances no other vessel is likely to approach her, either to divert and raw her off the enemy's fire, or give assistance in extinguishing the flames. It is possible that naval skill and genius may overcome some of these difficulties, but it is not probable that all of them could or would be surmounted, exposed as the vessel would be to quite formidable batteries in the fort, commanded by an officer (General Whiting) who is known to possess a knowledge of the efficiency of hot and hollow shot.

Admitting the probability of this vessel being satisfactorily moored at the selected site, nearest to the fort, and that the fuse explodes the powder at the desired moment, we find that the horizontal action of the powder thus exploded, whatever it may be, acts first upon the inclined plane forming the glacis of the fort, composed of a solid mass of earth more than 450 yards in length, and rising gradually to the height of twenty-six feet above low water. The armament of the fort is in part behind and below this hill. Back of it about sixty feet is a ditch filled