On Tuesday, the 20th of November, by request of General Lee, Montgomery Slaughter, Mayor of Fredericksburg, accompanied by the Recorder, William A. Little, Esq., and by Mr. Douglas H. Gordon, a member of her Council, held an interview with the Confederate Commander-in-Chief. It was held at Snowden, the residence of the late John L. Stansbury, about a mile above town. On Friday, the 21st, General E. V. Sumner, of the Federal Army, sent over a flag of trace, with a written message to the Mayor and Common Council of Fredericksburg. General Patrick, the bearer of the message, was met by Colonel Wm. A. Ball at "French John's" wharf, at the foot of Hawke street. General Sumner's letter, to the town authorities was as follows: "GENTLEMEN:--Under cover of the houses of your town, shots have been fired upon the troops of my command. Your mills and factories are furnishing provisions and material for clothing for armed bodies in rebellion against the Government of the United States. Your railroads and other means of transportation are removing supplies to the depots of such troops. This condition of things must terminate; and by direction of Major-General Burnside, commanding this army, I accordingly demand the surrender of the city into my hands, as the representative of the Government of the United States, at or before five o'clock this afternoon (5 o'clock P. M. to-day). Failing an affirmative reply to this demand by the time indicated, sixteen (16 hours) hours will be permitted to elapse for the removal from the city of women and children, the sick, wounded and aged; which period having elapsed, I shall proceed to shell the town. "Upon obtaining possession of the town every necessary means will be taken to preserve order and secure the protective operation of the laws and policy of the United States Government."