successful. The result of their investigation is set forth in the following extract from the reply made on the 6th, in compliance with the instructions received by them:

The enemy's front has been very much strengthened. It consists of a system of redoubts connected by infantry parapets. The ground in front in obstructed by abatis, stakes, and entanglements, rendering an assault impracticable. Regular approaches must therefore be resorted to. It is probable the siege will be a very long one, inasmuch as soon as one line of works is carried another equally strong will be found behind it, and this will continue until the ridge is attained which looks into the town.

The front of attack decided upon was a salient of the enemy's line on or near the Jerusalem plank road.

On the 9th of July orders were issued by the commanding general that "the operations of this army against the intrenched position of the enemy defending Petersburg will be by regular approaches on the fronts opposed to General Burnside's and General Warren's corps," and on the following day a plano conducting the siege was submitted.

On the 11th, the project, being in conformity with his views, was approved and adopted, and it was ordered that the work be commenced at once. Copies of the respective papers above referred to will be appended to this report.

The interesting reports of Captain Mendell, commanding the Engineer Battalion, and of Lieutenant-Colonel Spaulding, commanding detachment Fiftieth New York Volunteer Engineers, furnish summaries of the engineering work performed under the direction of the different officers of their respective commands in accordance with the plan of attack adopted.

Lieutenant Lydecker, who reported late in June, was retained on duty at general headquarters; also took an active part in the construction of the works referred to. Captain Farquhar had charge of those in front of the Eighteenth Corps. Descriptions of the several redoubts and batteries constructed are also therein given, and drawings of them will be submitted in the appendix to this report; the latter were made by Corporal Thompson, assisted by some non-commissioned officers and privates of the Engineer Battalion, under the direction of its commanding officer.

On learning the plan adopted I directed my principal assistant, Major John E. Weyss, to commence on the 9th an exact triangulation of the front of Petersburg, locating our own line of work as well as that of the enemy, and to take the immediate charge of the surveying party. My assistants, Messrs. Theilkuhl, Schumann, and Jacobsen aided him. The work was extended from the south of the Jerusalem plank road as far north as City Point. By this triangulation, performed under the fire of the enemy's batteries and sharpshooters, the different spires and certain prominent buildings in Petersburg were accurately located, and having been kindly furnished by Professor Bache, Superintendent of the United States Coast Survey, with a copy of the beautiful map of that city and the Appomattox River prepared a few years ago in his department, I was able to combine the two, and thereby obtain an exact and connected map of the locality of our siege operations, covering the whole ground occupied by both armies.

On the 9th the troops of the Sixth Corps were withdrawn from the line so long occupied by them and ordered to Washington City. On the following day I was directed to select a line, refused from the position occupied by that corps, extending from the redoubt (now called Fort Prescott, then in course of construction) on the Jerusalem plank