[Second indorsement.]

HDQRS. SECOND DIVISION, SIXTEENTH ARMY CORPS, April 10, 1865.

Brigadier-General Gilbert's brigade is assigned to this duty. He will report to General Canby for orders.

K. GARRARD,
Brigadier-General, Commanding Division.

HDQRS. FIRST DIVISION, SIXTEENTH ARMY CORPS, In the Field, near Blakely, Ala., April 10, 1865.

[Lieutenant Colonel JOHN HOUGH,

Assistant Adjutant-General:]

COLONEL: I have the honor to submit the following special report: During the recent siege of Spanish Fort, Ala., Bvt. Major General John Mc Arthur (commanding this division) designed and caused to be manufactured six 12-pounder wooden mortars, to be used on the skirmish line. These mortars were made from the gum trees found growing in the vicinity of the fort. Being light, the men carried them to the skirmish line in the advanced parallel, where they were set to bear upon the fort or any point in the front of the First Division lines. Upon experimenting with them it was found that they could be made to thrown shell with perfect accuracy. They were used with great success in throwing shell in the lines occupied by the rebel skirmishers; also great injury was done the enemy by throwing the shell and arranging the fuse to cause them to explode inside his works. They proved so essential and effective that the general caused sic more to be made of the same size, and one of 24-pounder caliber, but before these were placed in position the fort was taken. These were made by the pioneer corps of the First Division, and are so simple in construction that any mechanic of ordinary skill can make them. The satisfactory result of this experiment, the cheap and portable character of the materials, and their efficiency (being equal in this respect to brass mortars), demonstrates conclusively that wooden mortars can be used to beat advantage and that the subject is well worthy attention. The following is a description of the formation of the 12-pounder mortars: Length, 16 inches; diameter, 12 inches; depth of bore, 8 inches; diameter of bore, 4 1\2 inches. Three iron bands, on around muzzle, one at breech, and one intermediate. Through the band at the breech was drilled the touchhole. They are fixed in sticks of timber 12 by 8 inches, and 3 feet long, fastened on timber by hooks and staples; use from two to four ounces of powder, common shell, time fuse; length of fuse varied to distance, and friction primer. Mortars were fired----times and sustained no injury; yet serviceable for another siege.

I have the honor to be, colonel, very respectfully, your obedient servant,

H. B. STRAIT,

Major Ninth Minnesota Infantry Volunteers, Actg. Asst. Insp. General, First Division, Sixteenth Army Corps.

HDQRS. SECOND DIVISION, SIXTEENTH ARMY CORPS, Near Blakely, Ala., April 10, 1865.

Major General F. STEELE, Near Blakely:

GENERAL: Since my conversation with you this evening, and after learning of the contention in regard to the engagement of yesterday,