[Inclosure No. 2.] FORT POINT, San Francisco, June 10, 1863.
Brig General G. WRIGHT,
Commanding Department of the Pacific:
GENERAL: In compliance with the request contained in your department letter of the 8th of April last, I have examined and caused to be surveyed the sites on Yerba Buena Island and Rincon Point, which appeared to me to be the best adapted for the defenses of the inner harbor of the city. They consist of two positions on the island and the termination of Beale street on Rincon Point. Could the grounds upon which the U. S. Marine hospital is constructed be disposed of for a battery, it would decidedly be the most efficient one on or near Rincon Point, on account of its field of fire, but unfortunately the building would be too much exposed to the shots aimed at the battery. In case, however, of real necessity, a battery could be constructed on two sides of that building to co-operate with the battery proposed on Rincon Point. The battery on Rincon Point could be constructed from the center of Harrison street on Beale street to the precipitous bank on the bay, as is shown in the accompanying drawings, leaving a roadway of over twenty feet in its rear. Twelve guns can be placed in position there, leaving sufficient room for a magazine; 32-pounder guns are recommended for this battery. Its construction would involve but little expense; the breast height would only require a wooden structure of boards and scantling to sustain the earthen embankments, and the platforms would answer made of lumber. As it is supposed that the city or State will at its own expense erect these defenses, it is presumed that the civil engineers will make the necessary estimates. With regard to Yerba Buena Island, two sites have been selected, the first at the position marked "B" on the plan, and the second at the position marked "C".
The position "D" is looked upon as essential for a temporary redoubt or block-house, to protect the rear of the two batteries. The battery at "B" is so arranged as to have a field of fire that covers all the deep water within two miles of the island from north to south. the rear of the island in the direction of San Antonio is impassable for sailing vessels in consequence of shoals that extend from the island to the main, and it therefore is unnecessary to plant guns in that direction against shipping. It is proposed to mount ten heavy guns in this battery. On the point "C" it is proposed to erect a second battery, mounting eight 32-pounder guns. The excavations at this point will cost probably more than those at point "B", in consequence of the nature of the position, which is rocky and will require some blasting. The island, by the by, is very much of the same character, particularly on the side facing the city, which is composed of high rocky bluffs. The distance between Rincon Point and the island is about one mile and three-quarters. Should heavy guns or rifled ones be selected for the two batteries on the island and the one on Rincon Point, the cross-fire would extend from shore to shore and command the anchorage within the reach of the batteries. Supposing that it would be agreeable to you to have a general map of the whole harbor, with the several positions selected for its defense traced thereon and the field of fire from each indicated by circles drawn every half mile to a distance of two miles, including the number of guns bearing in each direction, I have caused to be compiled from drawings, in this office a map of that kind for your headquarters.
Not found as an inclosure.