The dimensions of the crater proved to be 200 feet long and 50 feet wide, the explosive charge being 8,000 pounds. The grand assault was made, and the accomplish its purpose. Orders were issued to discontinue operations during the day.

Accompanying this report are those of Colonel Spaulding and Captain Mendell, both already referred to, together with the several papers* ordering and planning the siege operations in front of Petersburg. Appended to it is also a portfolio of maps,+ with a table of distances ++ between the separate camps of the major-general commanding.

The following list comprises the several numbers of each of the series, namely:

A. Six sheets (1-6 inclusive), campaign maps showing in colors the lines of operations of the several corps of the Army of the Potomac, from the neighborhood of Culpeper to the front of Petersburg.

B. Eleven sheets (1-11 inclusive), copies of photograph maps as issued to the army during the entire campaign.

C. Four sheets (1-4 inclusive), battle-field maps, Wilderness, Spotsylvania, Cold Harbor, siege of Petersburg.

D. Seven sheets (1-7 inclusive), drawings, plans, and sections of redoubts and batteries, constructed during the month of July in front of Petersburg.

E. Eleven sheets (1-11 inclusive), drawings showing the first and advanced line of the enemy in front of Petersburg, with plans and sections of batteries along it.

F. Six sheets (1-6 inclusive), copies of the original campaign maps compiled from the best authorities for the use of the Army of the Potomac previous to the commencement of the move across the Rapidan.

This report does not intend to furnish more than a general outline of the various duties performed by the different officers of the Engineer Corps who were during the campaign connected with the Army of the Potomac. As far as it has been in my power, I have endeavored to portray faithfully the extent of their labors. Many omissions may have been made in enumerating them, but these may be rectified in a subsequent and more detailed account of that most interesting period, when time and circumstances allow an exact description to be furnished of the country through which the lines of march extended, and of the nature of the operations performed.

I have not deemed it proper or right to dwell upon the exact character of the duties performed by the acting chief engineer, Major James C. Duane, only casually having mentioned them in a few cases when we accompanied each other on different reconnaissances. It is to be hoped that his health will soon permit him to prepare an accurate statement of the engineering operations performed by him and under his directions. Until then I trust that what has now been presented will prove acceptable. Believing it would afford him great pleasure, in his name I respectfully request the favorable attention of the major-general commanding to the important services rendered by the officers of both the regular and volunteer engineers. They labored faithfully and earnestly to attend to the respective duties assigned them, and I believe with great credit and honor to themselves and to that arm of service to

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*See Meade, to Hunt and Duane, July 3, Part II; Hunt and Duane to Humphreys, July 6, p. 285, ante; same July 10, p. 286, ante; Orders, July 9, p. 159, ante; and Williams to Hunt and Duane, July 11, p.287, ante.

+Such of these maps as may be found will appear in the Atlas.

++See Vol. XXXVI. Part I, p.303.

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