I send you a paper on the defence of the mouth of the Chesapeake. We never expect from the writer a detailed, well-digested and practicable plan; but good ideas and susceptible of improvement sometimes escape from him. The first question is, whether works on the shore of Lynhaven may not be constructed for dislodging an enemy from that bay by throwing bombs? and whether they can lie there in safety out of the reach of bombs? There is no other place where they can lie in safety so near the Capes, not to be in danger of being intercepted by gun-boats, and attacked with the advantage of weather. 2d. May not artificial harbors be made on the middle grounds and Horseshoe for the reception of gun boats, with cavaliers for the discharge of bombs? and will not these two points and Lynhaven thus command all the mouth of the bay? To answer these questions will require an accurate survey of the whole field, which, if we have not, we should direct to be made. It is an important fact that the middle grounds have been seen bare; and that both these and the Horseshoe are always shoal. Cannot cassoons filled with stone, and of the shape of truncated wedges, be sunk there in close order so as to enclose a harbor for gun-boats, of such a height as that the sea shall not go over it in the highest tides, and of base proportioned to the height and sufficient to resist the force of the water? The nearest stone is up James river above the Hundred, and up York river above West Point, from whence however it can be brought in ships of size. At New York, they calculate on depositing their stone for from 4 to 5 cents the cubic foot. If it costs the double here, the amount would not be disproportioned to the object, if we consider what a vast extent of coast on the Chesapeake and its waters will otherwise be depredated or secured by works and troops in detail. I throw out these thoughts now that they may be under your consideration, while making up the general statement of defensive works for the sea coast. Present my respects to Mrs. Dearborne, and accept my affectionate salutations. TO THE SECRETARY OF STATE. MONTICELLO, September 1, 1807. DEAR SIR,--I think with you we had better send to Algiers some of the losing articles in order to secure peace there while it is uncertain elsewhere. While war with England is probable, everything leading to it with every other nation should be avoided, except with Spain. As to her, I think it the precise moment when we should declare to the French government that we will instantly seize on the Floridas as reprisal for the spoliations denied us, and, that if by a given day they are paid to us, we will restore all east of the Perdido, and hold the rest subject to amicable discussion. Otherwise, we will hold them forever as compensation for the spoliations. This to be a subject of consideration when we assemble.