U. S. STEAME SAN JACINTO, November 15, 1861.

Honorable GIDEON WELLES, Secretary of the Navy.

SIR: I have written to you relative to the movements of this ship from Cienfuegos on the south coast of Cuba. There I learned that Messrs. Slidell and Mason had landed in Cuba and had reached the Havana from Charleston. I took in some sixty tons of coal and left with all dispatch on the 26th of October to intercept the return of the Theodora; but on my arrival at the Havana on the 31st I found she had departed on her return and that Messrs. Slidell and Mason with their secretaries and families were there and would departhe month in the English steamer Trent for Saint Thomas on their way to England.

I made up my mind to fill up with coal and leave the port as soon as possible to await at a suitable position on the route of the steamer to Saint Thomas to intercept her and take them out.

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I then went over to Key West in hopes of finding the Powhatan or some other steamer to accompany me to the Bahama Channel to make it impossible for the steamer in which Messrs. Slidell and Mason were to embark to escape either in the night or day. The Powhatan had left but the day before and I was therefore disappointed and obliged to rely upon the vigilance of the officers and crew of this ship and proceeded the next morning to the north side of the island of Cuba, communicated with Sagua la Grande on the 4th, hoping to receive a telegraphic communication from Mr. Shufeldt, our consul-general, giving me the time of the departure of the steamer.

I this also I was disappointed and ran to the eastward some ninety miles, where the old Bahama Channel contracts to the width of fifteen miles some 240 miles from the Havana and in sight of the Paredon del Grande Light-House. There we cruised until the morning of the 8th awaiting the steamer, believing that if she left at the usual time she must pass us about noon of the 8th and we could not possibly miss her. At 11. 40 a. m. on the 8th her smoke was first seen. At 12 m. our position was to the westward of the entrance into the narrowest part of the channel and about nine miles northeast from the light-house of Paredon del Grande, the nearest point of Cuba to us. We were all prepared for her, beat to quarters, and orders were given to Lieutenant D. M. Fairfax to have two boats manned and armed to board her and make Messrs. Slidell, Mason, Eustis and Macfarland prisoners and send them immediately on board. (A copy of this order to him is herewith inclosed.) The steamer approached and hoisted English colors. Our ensing was hoisted and a shot was fired across her bow. She maintained her speed and showed no disposition to heave to. Then a shell was fired across her bow which brought her to. I hailed that I intended to send a boat on board, and Lieutenant Fairfax with the second cutter of this ship was dispatched. He met with some difficulty and remaining on board the steamer with a part of the boat's crew sent her back to request more assistance. The captain of the steamer having declined to show his papers and passenger list a force became necessary to search her. Lieutenant James A. Greer was at once dispatched in the third cutter also manned and armed.

Messrs. Slidell and Mason, Eustis and Macfarland were recognized and told they were required to go on board this ship. This they objected to until an overpowering force compelled them; much persuasion was used and a little force and at about 2 o'clock they were