It is of the greatest importance that all the disposable force under your command should be concentrated with dispatch upon the Sabine.

Colonel Herbert will communicate more fully with you upon the subject .

I am, general, very respectfully,

W. R. BOGGS,

Brigadier-General and Chief of Staff.

ENGINEER'S OFFICE, Galveston, April 30, 1863.

Captain EDMUND P. TURNER,

Assistant Adjutant-General, Brownsville:

CAPTAIN: I have the honor to make the following report for the month of April, 1863:

Fort Point-casemated battery.-The wood, iron, and earth work was completed during this month; five iron casemate constructed; the guns mounted; cisterns placed, and hot-shot furnace constructed. It has to be sodded all over, the bank being high and composed of sand. Two 10-inch mortars will be placed on the top behind breastworks.

Fort Magruder-heavy open battery.-The front embankment, traverses, platforms, and magazines were completed during this month; two 10-inch columbiad mounted. The Harriet Lane guns are not mounted, for want of suitable carriages, which are under construction. Bomb-proofs and embankment in the rear commenced and the front embankment sodded inside, top and slope. With the present force it will require nearly the whole of this month to complete it.

Fort Bankhead.-Guns were mounted and the railroad constructed during this month.

South Battery.-For want of labor the reconstruction of this battery was commenced within the last few days of the month; also the construction of the railroad leading to it.

Entrenchment of the town is barely commenced, for want of labor.

Obstructions in the main channel.-Since the destruction of the rafts by storm, before they could be fastened to the abutments, this plan of obstruction had to be abandoned for the want of material to repair the damage done. The present system of obstructing consists of groups of piles braced and bolted and three cable chains fastened to them, the groups of piles in the deepest part of the channel to be anchored besides. This was the first plan of obstructing the channel on my arrival here; but being informed by old sailors and residents that piles could not be driven on account of the quicksand, and not having the necessary machinery then to examine the bottom, it was rejected. Having constructed a machine for this purpose, it is certain that piles can be driven and are actually already driven half across. This obstruction will be completed and the chains stretched from abutment to abutment by the 10th of May. Sketch, letter A, represents the work.

Obstructions at the head of Pelican Island.-Two-thirds done. It will require the whole of May to complete this obstruction and erect the casemated sunken battery of two guns, as proposed in my last report. These works are greatly retarded by the difficulty of procuring the material.

Pelican Spit to be fortified, as submitted in my last report, with a casemated work. For its defense two 32-pounders and one 24-pounder can be spared. This work is of great importance, but it had to be postponed until the entrenchments around the town shall be fairly advanced.