in reference to the defenses of San Frncisco Bay and to the works disegned for Alcatraz Island: The forts designed for Fort Point and Lime Point ocnstitute the primary line of defense for the entranceto San Frnacisco Bay and Harbor. When completed they will command the strits one mile wide, with a powerful array of guns, and it may be presumed that no ordinary expedition of an enemy will attempt to pass these batteries in clear weather by daylight. Fogs, however, are quite a characteristic feature of the weather of this coast; moreover, the entrnace to the bay is not only practicable, but quite easy at night, being favored by the strong westerly trade winds, and opposed by o natural obstructions. Further, the objects to be reached, viz, the arsenal at Benicia, the navy- yard at Mare Island, the city of San Frnacisco, and the possession of the only important harbor on the Pacific Coast, would justify an extraordianry expediton on the part of a powerful maritime enemy, and the risk of a very considerable loss in attaining its aim; hence the necessity for a secondary line of defensive works for the bay of San Francisco. These works are designed tos hut up Rccoon Straits, t he pass between Angel Island and thenorth shore of the bay; alsothe passage between Angel Island and Alcatraz, and that between Alcatraz and San Francisco. The most prominent position of this secondary line is Alcatraz Island. Its guns sweep a larger expanse of waters than those of any other point, and it leis upon the two passes of ingress and egress most readily navigated. It has additional importance at this time form the advanced state of its batteries as compared with those of the outer line, and from the fact that the same expediture which would simply prepare the foundations foa the fort designed for Lime Point would finish all the batteries upon Alcatraz, together with its defensive lines, s o as to secure the island against any attack that might be made upon it. The position next in importance uponthe secondary line of defense of San Francisco Bay is Point Stewart. Batteries upon this point will effectually command Raccoon Straits within short range, will prevent ships from lying at anchor in Saucelito Cove, and will cross thrir fire with the northwest batteries of Alcatraz Island. When the works at Fort Point, at Alcatraz, and at point Stewart are finished, the primrry and secondzary lines of defense will be closed, and all the waters between them brought under fire, and it is probable that no ordinary expedition would attemtp to force these lines, s trngthened as they might readily be by temporary batteries at Point San Jose, near San Francisco, point Blunt, on the southeast end of Angel Island, and Point Caballos, just within Lime Point. THese batteries could be constructed wiof ordinary intrenchments revetted with sand- bags. The full sustem of defense requires the construction of the work designed for Lime Point and the erection of permanent batteries at point San Jose and Point Blunt. Point San Jose is within the city of San Francisco. The battery required at this point will be in barbette, with earthen parapet, breast height of bricks, a small magazine, and a brick building for ordnance stores and fora guard house. It should mount twenty guns. A similar barbette battery will suffice to occupy Point Blunt, on Angel Island, but this position being more isolated should be held by a keep or defensive barrack; the aattery should be prepared for twenty- five guns.

Point Stewart should be occupied by a permanent barbnette battery, so defended as to be secure against any attack that might be urged against it. The particular character of this work is not yet determined, as the ground has not been surveyed. it will be surveyed and reported upon without delay. The westerly trade winds previoulsly mentioned continue eight months of the year. They blow directly into the Bay