SIR,--I have to acknowledge the receipt of your letter of the 7th instant, on the subject of the British ship Rochampton, taken and sent into Baltimore by the French privateer the Industry, an armed schooner of St. Domingo, which is suggested to have augmented her force at Baltimore before the capture. On this circumstance a demand is granted that the prize she has made shall be restored. Before I proceed to the matters of fact in this case, I will take the liberty of calling your attention to the rules which are to govern it. These are, I. That restitution of prizes has been made by the Executive of the United States only in the two cases, 1st, of capture within their jurisdiction, by armed vessels, originally constituted such without the limits of the United States; or 2d, of capture, either within or without their jurisdiction, by armed vessels, originally constituted such within the limits of the United States, which last have been called proscribed vessels. II. That all _military equipments_ within the ports of the United States are forbidden to the vessels of the belligerent powers, even where they have been constituted vessels of war before their arrival in our ports; and where such equipments have been made before detection, they are ordered to be suppressed when detected, and the vessel reduced to her original condition. But if they escape detection altogether, depart and make prizes, the Executive has not undertaken to restore the prizes. With due care, it can scarcely happen that military equipments of any magnitude shall escape discovery. Those which are small may sometimes, perhaps, escape, but to pursue these so far as to decide that the smallest circumstance of military equipment to a vessel in our ports shall invalidate her prizes through all time, would be a measure of incalculable consequences. And since our interference must be governed by some general rule, and between great and small equipments no practicable line of distinction can be drawn, it will be attended with less evil on the whole to rely on the efficacy of the means of prevention, that they will reach with certainty equipments of any magnitude, and the great mass of those of smaller importance also; and if some should in the event, escape all our vigilance, to consider these as of the number of cases which will at times baffle the restraints of the wisest and best-guarded rules which human foresight can devise. And I think we may safely rely that since the regulations which got into a course of execution about the middle of August last, it is scarcely possible that equipments of any importance should escape discovery.