To-day Jones is building a bridge over the canal, so as to cross right from the ford. This looks like preparations for the cavalry retrograde by and by, and I think it probable Ewell may fall back on the Winchester line; at all events, it looks like it. This moment the signal officer reports camp fires in the direction of Williamsport. This bridge is significant. He cannot use it now, as his troops have already passed. It is represented to be constructed with very heavy sills, and he was hauling planks to cover it with. My impression is that Jones means to hold this position until he sees if Ewell will require it in any retrograde he may make. In other words, I think Jones is remaining here to cover Ewell's possible retreat. Will investigate to-morrow.

DAN. TYLER,

Brigadier-General.

JUNE 18, 1863-10 p. m.

Major-General SCHENCK:

General Hooker requests that you will advise him where your troops are stationed, their character, and number.

DANL. BUTTERFIELD,

Major-General, Chief of Staff.

WASHINGTON, D. C., June 18, 1863.

Major-General SCHENCK, Baltimore, Md.:

General Heintzelman's scouts, in the vicinity of Poolesville, have reported no enemy in force. Anything that occurs there will be reported to you.

H. W. HALLECK,

General-in-Chief.

BALTIMORE, June 18, 1863.

Captain P. R. STETSON, Fifteenth Infantry, Harrisburg:

The Seventh New York State Militia is here, but Colonel Lefferts says they have no battery gone to Harrisburg, nor any battery whatever left New York. There must be some mistake.

DONN PIATT,

Lieutenant-Colonel, and Chief of Staff.

CAMDEN STATION, Baltimore, June 18, 1863.

(Received 1. 45 a. m.)

Honorable E. M. STANTON,

Secretary of War:

A train sent to Harper's Ferry yesterday a. m., with troops and supplies, which left Sandy Hook for Baltimore at 5 last p. m., has been captured and burned at Point of Rocks. It consisted of a first class engine and 22 cars. Our operator reports that the enemy were 400 of White's cavalry, and that they also captured and carried off