which left at 10 a. m. this morning. The whole of the rebel army is by this time at least as far as Hagerstown to-morrow.

The whole of the rebel army have taken the pike toward Hagerstown, and I believe they are making rapidly, but in tolerably good order, toward Williamsport.

Captain [George C.] Cram, now prisoner of war at Monterey, states that the discipline of the enemy seems to be very much relaxed. In the last two days I have taken a great many prisoners, or, rather, deserters, from the rebels.

Very respectfully,

THOS. H. NEILL,

Brigadier-General, Commanding Light Division.

HEADQUARTERS CHIEF ENGINEER OF DEFENSES, Washington, July 7, 1863.

Colonel J. C. KELTON,
Assistant Adjutant-General:

COLONEL: In November and December last, a commission of officers, appointed by the War Department, investigated and reported upon the Defenses of Washington, recommending additional works at certain points they deemed weak; the perfection and improvement of other works; and the building of two water batteries for the protection of the city against naval attack.

To carry out these suggestions (approved by the War Department), I asked for and obtained an appropriation of $200, 000.

The work has been prosecuted with all the vigor the means at my disposal would admit. Although the winter season was most unfavorable for such work, and with the limited amount of money available, as well as with regard to economy, it was not deemed advisable to employ very large gangs of hired laborers, yet, by aid of the troops, working whenever the weather and state of the ground would permit, the most essential works recommended by the commission, such as the advanced works around Fort Lyon; Fort Williams, on Traitor's Hill; Forts Whipple and C. F. Smith, on the Arlington lines; the additional works at the Chain Bridge; the union of Forts Alexander, Franklin, and Ripley into one (Fort Summer); the completion and construction of Forts Mansfield, Simmons, and Bayard; the modifications of Forts Reno, De Russy, and Stevens; the extension of Fort Slocum, &c., and the connecting system of rifle-pits and batteries for field guns, were all pressed forward, so as to be in a condition, if not complete, at least of efficiency, for their uses, with the return of the season, when active field operations might throw Washington upon its defenses.

The two water batteries were commenced in May, one of them, being out of the line, requiring a very expensive work to render it self-sustaining. My estimates, however (so far as I could estimate at all), were founded upon my previous experience, in which I had been aided freely by troops, and I counted on their aid in doing most of the earthwork and rifle-pits.

Instead of this, however, as soon as the season favorable for work actually set in, almost every detail of troops was withdrawn. The extensive system of rifle-pits, incomplete and demanding thousands of men, was left for me to complete unaided.