HDQRS. CITY GUARD, PROVOST-MARSHAL'S OFFICE,
Washington, D. C. January 9, 1862.

Brigadier General A. PORTER, Provost-Marshal, Washington, D. C.

GENERAL; I have the honor to report that on December 21, 1861, Michael Thompson, attorney at law of this city, was arrested and confined in the Old Capitol under the following circumstances: On the arrest of Mrs. R. Greenhow August 23, 1861 the fragments of a note to her from one G. Donellan were found in her stove, which showed that it has but recently been destroyed. This Donellan had formerly been employed as a clerk in the Department of the Interior. He was then engaged with her in forwrding treasonbale communication to the rebels andis now in one of the departmeners of the rebel Government at Richmond. A copy of the above note is subjoined;

PRIVATE.] SATURDAY MORNING, July 20, 1861.

Mrs. R. GREENHOW, Present.

MADAM: I depart this morning regretting my inopportune absence; however, there is something to convey which I trust may prove valuable at least. Colonel Thompson, the bearer, a true South Carolina gentleman, will be happy to take from yoru hand any communication and obey your injunction as to disposition of same with dispatch. It may not be too late immediately you return to ascertain something important regarding the movements of the two or three next succeeding days, and I apprehend there will be something worth dispatching. Colonel T[hompson] will verbally inform you of the extent of my information now and what I conjecture will be done inorder to acquaint you of what will be communicated.

Very respectfully,

G. DONELLAN.

On finding the above letter I perceived the necessity of ascertaining who Colonel Thomspon was, and consequently directed operations to this end, detailing one of my operatives to attend to this. In the investigations thus rendered necessary my operative became acquainted with a Mrs. Phelps from whose own avowals to himproof was obtained of her treasonable sentiments and intentions. She also expressed herself particularly anxious to apprise the charleston people of the supposed destination of DuOur operative, passing himself as a Georgia secessionist, said he would make a determined effort to convey said information, and that he should succeed if she would introduce himto some of our friends here who were right on Dixie. She replied that Colonel Michael Thompson, a South Carolina lawyer in her confidence, was all right. She offered personally to introduce our operative to him, which the latter declining she gave hima letter of introduction, telling him to speak plain to Thompson as he (Thompson) could be trusted.

Shortly afterward our operative was informed by Mrs. Phelps that Mr. Thompson was very anxious to see him and had asked her if she was sure her Georgia friend (my operative) was not a spy on them, "as," said Mr. Thompson, "the Government detectives are trying all those games. " He also remarked that she ought to be very careful whom she trusted, &c. Not deeming it policy at that time that my opoerative should thus become personally acquainted with Thompson an excuse was at that time made to Mrs. Phelps setting forth the urgent necessity of my operative to return South, and with expressions of deep regret on his part that he could not at that time become acquainted with Colonel Michael Thompson he left Mrs. Phelps on his supposed return to the rebel States.

Having thus found that Michael Thompson, attorney at law, 432 G street, was to be relied on as safe to talk with on treasonable subjects and also for forwarding correspondence with the rebels the conclusion