Jackson and Saint Philip ten rifled 30-pounders, ten rifled 100-pounders, and four 15-inch guns.

At Forts Pike and macomb there should be two rifled 30-pounders each; at Ship Island, two rifled 100-pounders.

The board also recommends that the main depot for ordnance stores and other material be in citadel at New Orleans, and secondary deports at Port Hudson and Baton Rouge.

The approaches to the city of New Orleans by water are so numerous that no system of defense can be completed without the co-operation of a large naval force.

Adjourne sine die.

D. C. HOUSTON,

Major, and Aide-de-Camp, Captain U. S. Engineers.

W. B. FRANKLIN,

Major-General of Volunteers.

PORT HUDSON,

August 13, 1863.

Lieutenant Colonel RICHARD B. IRWIN,

Assistant Adjutant-General:

COLONEL: With reference to the proposed fortifications at Port Hudson, I have the honor to submit the following statements and report:

I have been verbally authorized by General Banks to proceed to fortify the place according to my own judgment in the case. I have already given to General Banks, General Stone, and Major Houston an outline of my views on the subject. It appears to me that the opinion I have on the subject, after much consideration, and with very favorable opportunities for studying he ground, and not be without interest to the commanding general.

The plateau in the center of the present fortification is about 1,000 yards long, in a direction parallel with the river bank, and about 650 yards wide from the edge of the river bank back. It is very irregular, being surrounded by a ravine with very crooked ---; so crooked that it is difficult to sweep them with artillery. I suppose the garrison would not ordinarily, at least, during the season of active operations be very large - perhaps two or three regiments and some artillery. When the garrison should be large, the present works, somewhat repaired, with the addition of some redoubts at the important points, would admit of a very good defense; but in the usual state of the garrison a smaller work of much stronger profile would be necessary. A line of detached works under these circumstances would not, it appears to me, be as strong as a single strong work. I would, therefore, respectfully recommend the construction of a work, of strong profile, of from 1,500 to 2,000 yards' length of interior crust, with a covered way of profile strictly necessary, made partly in excavation and partly in embankment, so arranged as to be completely under the fire of the main works. For the defenses of the ravine, I would recommend simple rifle-pits, placed along the crest of the ravine, with a few small re-doubts in which to place field or siege artillery, the whole to be swept by the fire of the main works.

I would recommend for the armament, in addition to the smooth-bore guns which may be deemed necessary, from six to ten 30-pounder Parott guns, to be used to dismount the enemy's guns in batteries which he may attempt to establish against the works.