SIR: Certain matters have come to my notice, and considered by me, which induce me to believe that it will conduce to the public interest for you to add to the general instructions given to our naval commanders in relation to contraband trade propositions substantially as follows, to wit: First. You will avoid the reality, and as far as possible the appearance, of using any neutral port to watch neutral vessels, and then to dart out and seize them on their departure. NOTE.--Complaint is made that this has been practiced at the port of St. Thomas, which practice, if it exists, is disapproved and must cease. Second. You will not in any case detain the crew of a captured neutral vessel or any other subject of a neutral power on board such vessel, as prisoners of war or otherwise, except the small number necessary as witnesses in the prize court. NOTE.--The practice here forbidden is also charged to exist, which, if true, is disapproved and must cease. My dear sir, it is not intended to be insinuated that you have, been remiss in the performance of the arduous and responsible duties of your Department, which, I take pleasure in affirming, has in your hands been conducted with admirable success. Yet, while your subordinates are almost of necessity brought into angry collision with the subjects of foreign states, the representatives of those states and yourself do not come into immediate contact for the purpose of keeping the peace, in spite of such collisions. At that point there is an ultimate and heavy responsibility upon me. What I propose is in strict accordance with international law, and is therefore unobjectionable; whilst, if it does no other good, it will contribute to sustain a considerable portion of the present British ministry in their places, who, if displaced, are sure to be replaced by others more unfavorable to us. Your obedient servant, ABRAHAM LINCOLN. EXECUTIVE MANSION, _Washington, July 30, 1863_. It is the duty of every government to give protection to its citizens, of whatever class, color, or condition, and especially to those who are duly organized as soldiers in the public service. The law of nations and the usages and customs of war, as carried on by civilized powers, permit no distinction as to color in the treatment of prisoners of war as public enemies. To sell or enslave any captured person on account of his color, and for no offense against the laws of war, is a relapse into barbarism and a crime against the civilization of the age. The Government of the United States will give the same protection to all its soldiers, and if the enemy shall sell or enslave anyone because of his color the offense shall be punished by retaliation upon the enemy's prisoners in our possession.