for 956 guns, and of 93 batteries, having emplacements for 491 guns, and of 35,711 yards of infantry parapet or covered way; to which should be added about 33 miles of military roads, which have been built for purposes of communication where the existing roads of the country would not fulfill that purpose. A mere statement like this of the number of these works will convey some idea of the magnitude of undertaking to defend a great city, when it is essential to preserve it on account of its being the seat of Government, containing the Government machinery, from the long-rang guns of modern artillery. And such a statement will be apt to convey to all unmilitary minds the idea of enormous strength, a strength vastly greater than we actually possess. It should be borne in mind that these works are stretched out over a long line, some 37 miles in extent, inclosing the cities of Washington, Georgetown, and Alexandria, and that we have, in most cases, only a single line of defense, which, if once forced by an enemy, we have nothing between him and the public building and archives but our reserves, with the chances of battle in the open field. This consideration ought to show us the necessity of making this line a strong one; and if it does not suggest and additional interior line of defense, it will, at least, convince us of the necessity of having at all times, when there is a possibility of attack, the forts well garrisoned with practiced artillerists and a strong reserve within the defenses. In other words, if we should be attacked by a powerful army, Washington city would become, in a military sense, not a walled city with gates, but a great entrenched camp, requiring a large army for its defense, the defensive works standing for a certain number of men, enabling, perhaps, all other things being equal, 25,000 men in them to repel the attacks of 50,000, or 50,000 to repel 100,000, or 100,000 repel 200,000.

With these remarks, I proceed to a report of the work on the defenses during the past year. I will first take up the defenses south of the Potomac. these consist of thirty-one first, having an aggregate crest lien of 12,504 yards, with emplacements for 540 guns, and 42 batteries, having emplacements for 229 guns,a nd 20,869 yards of rifle-pits or coverer way for infantry. This includes only work now essentially completed or ready for its armament, and does not embrace work partially completed or in contemplation.

The present actual armament is 377 guns and 36 mortars. The work done during the past year-or from October 1, 1863, to September 30, 1864-can best be detailed by taking up each fort separately.

Fort Marcy: The front parapet has been raised and newly rivetted, new platforms and embrasures made, terre-plein graded and paved, gutters laid, new magazine made, abatis repaired, and the interior of the fort sodded.

Fort Ethan Allen: The abatis has ben removed, most of the embrasures newly rivetted with gabions, platforms repaired, and a new bombproof 230 feet long has been built; the southwest bastion has been cut off from the main work by a line of stockade, with gateway; one of the old magazines has been rebuilt, and a new bomb-proof guard-house constructed.

Fort C. F. Smith: This work, nearly completed at date of last report, has been completed and sodded.

Fort Strong: A new bomb-proof 280 feet long has been constructed, parapets re-enforced and newly rivetted, scarp built up from bottom of ditch on 45 degrees slope, three new traverses built, and the interior of fort sodded, and new platforms and embrasures made.