about fourteen feet in width, the outer embankment of which is elevated so as to reach nearly to its top. The entire works inside of this ditch are said to contain twenty-six acres of land.
From the bottom of the moat to the top of the principal rampart the height is about sixty feet, upon which is mounted about eighty pieces of artillery, upon a flat roof seventy feet wide by the whole extent of the wall. This flat roof is supported by arches, adjoining each other, twenty feet wide by seventy in length, and each one opening with a door upon the inside of the castle. These arches, adjoining each other and extending entirely around the square, constitute the workshops, storerooms, and cells of the prisoners. These cells are regularly numbered, and when the castle was completed in 1773, Ferdinando VII. was inscribed over each door in large letters. The ruthless hand of revolution has run the paint-brush over the name, though it is yet discernible through the painting. Upon the inner side, and at each angle of the fortification, is a broad stairway ascending to the top. These stairways are secured by strong wooden gates about twelve feet high.
Upon the inside of this fortification, and sixty feet between, is another range of square buildings, two stories high, the upper apartments of which are used as officers' quarters, soldiers' barracks, &c. This building opens upon a centre court, which is reserved for the military parade. The courtyard is about five hundred feet square, paved with cement, underneath which is an immense water-tank, containing many millions of gallons, supplied by a subterranean stream of water as pure as ever flowed from the  mountains: connected with this great water-tank are gates, by which, we were told, the moat may be flooded at the shortest notice. These works were the labour of many years; they cost many millions of dollars; and had not the improvement in the combustible shot formed a new era in the science of war, it would have been impregnable to assault.
We found our countrymen of Bexar occupying two of these long, narrow, dark archways, adjoining each other, in the eastern rampart of the castle. These arched cells are twenty feet wide by seventy long, with a door opening upon the inner side of the castle, and a loophole at the extreme end of the room, four by twelve inches, and widening through a wall eight feet thick to about two feet on the inside. When the doors are closed, which usually takes place at six o'clock in the evening, the prisoners are counted, and a sentinel placed at each door. The only ray of light admitted into this dark abode from without is through the loophole and a narrow grating over the door. The archways over head are fifteen feet thick, which support the artillery, underneath which are subterranean water-works, magazines, &c.
Upon the left of our Bexar friends, the adjoining rooms were occupied by their own Mexican chain-gang, a large number of convicts condemned to different