The ditch of the half-curtain (of which mention was reserved for this place, in order to avoid confusion) is formed by the waters which overflow from the river at the rise of the tides. It starts from the angle defended by the bastion San Gabriel, and extends until it is very near the Parian gate, with a counterscarp--which there leaves it, bending toward the crown-work, and thus is left almost isolated, with a small arm. This, a little farther, adds all its waters, as if on deposit, to the outer ditch already mentioned. Not thus the main ditch; for this, overflowing the right side according to the amount of water which it receives [from the river], continues its course along the margin of the grand highway, more or less closely according to its curves, until, coming close to the walls, it ends its course round about them, close to the bastion San Diego. At this place art has imposed restraints on it, having in mind, no doubt, the frequent inundations to which that vicinity would be exposed if (as was easy for it) this ditch should come to unite its waters with the sea. From this measure of prudence resulted two benefits of special importance, in which both the fortified post and the public are directly interested--the former, on account of the advantage which it enjoys (as may be seen in the plan) in the fact that the ditch serves it as a moat on the eastern and southern sides; and the latter, because it is utilized for the great number of vessels which, aided by the rising tide, come up to the Puerta Real to discharge their lading. This is one of the two principal gates already mentioned. It is located on the southern side of this town, in the curtain which defends the bastions San Diego and San Andres, although nearer to the latter; and it much resembles the gate of the Parian (although built in different style) in its convenience and its fortifications--for it has, like the former, a guard-station and watchtower, similarly arranged and equipped. It is only noted that this curtain, peculiar among all, is the only one which is furnished with terreplein; for this reason some cannons (which defense the others lack) have been placed in it. Its other exterior works, arranged according to their order, are reduced to a bridge that can be raised, a moat with its counterscarp faced with stone [revestido], and at a little distance a ravelin in condition for defense--notwithstanding which, on account of masking the gate it is not found in front of the half of the curtain which was its proper place. Although this gate had the remaining features of covered way, parapet, palisade, and esplanade, they were entirely in ruins at the time when this government began--which induced us to plan them anew, in modern style, and of much better quality than were the old ones.