If the additional man be required in the gallery and two extra men at the shaft to each relief, this will increase the force to forty-eight men. When the mines are extended, as is now the case at Colquitt's, so that an extra self of men can work in an additional gallery, an additional force will be required of one miner, one shoveler, two wheelers, and two men at the shaft, or a total force of twenty-four men. One non-commissioned officer can take charge of the two reliefs and work them, each detachment going in charge of a commissioned officer. The reliefs generally prefer to work out their full time and then to go off duty; this gives them eighteen hours to rest. At Gracie's mine two detachments are required, as only one mine can be extended judiciously at this point. At Colquitt's four detachments can work, two reliefs working together in the mine, driving forward two galleries. At Pegram's two detachments are as full a force as can be judiciously worked.

Very respectfully, your obedient servant,

HUGH THOS. DOUGLAS,

Captain, Engineer Troops, in Charge Mining, &c.

ENGINEER CAMP, August 2, 1864.

Captain H. T. DOUGLAS:

CAPTAIN: I have the honor to make the following report of operations and observations at the crater made by the explosion of the mine on Saturday morning last:

When you and myself made a partial examination of the Crater on Saturday afternoon we found it so full of the enemy's dead and wounded that nothing could be accomplished then toward discovering the gallery through which the enemy sprung the mine. On Saturday morning, July 31, 1864, I proceed to the scene of the explosion with ten men and at once commenced work, sinking a shaft. At 12 m. you sent me another detachment of then men, and I commenced another shaft at the north end of the Crater and another at the south end. I worked until 7 p. m. without finding anything important. I took another detachment down on Monday. Upon examination of the shaft at the north end I noticed a small crater, which I supposed to be one of the enemy's chambers. The bottom of this shaft is about twenty-four feet from top of the present parapet. At 6 p. m. there were three small excavations on right, left, and center of shaft, which I think have something to do with one of the enemy's smaller galleries. Have discovered nothing in the other two shafts. My opinion is that the main gallery comes from the right of the enemy's lines. Did no work last night, it being dangerous from fear of sides of shaft caving in.

E. N. WISE,

First Lieutenant, Engineer Troops.

HEADQUARTERS, August 3, 1864.

His Excellency JEFFERSON DAVIS:

You will receive a letter from me by courier to-morrow morning. If after that you think it desirable I will go to Richmond.

R. E. LEE.