A private letter says the naccessibility and difficult nature of the approaches to the parapet had been very f'ully impressed on my mind before, and I then was entirely satisfied that no suoh place had ever before been so adapted by Nature herself for an impregnable fortress. - The works are some üvo miles in length extendicg from one point on the river to another some miles above. This line of works is fronted ou all sides for a mile (and in some places two miles) back, with ravines some rifteen or twenty feet deep and wide, and filled with brush and felled trees completely, and so close together that I can give you no better idea of thern than to have you place both hands on a table, and spreading out the íingers, imagine the spaces between to be the ravioes. Many of them would be almost of themselves, if clear and free of obstados, sufficient to prevent any passage, but choked as they are, it is irapossiblo to clamber through them, except,with as much labor as it would be to go through a forest by way of the tops of the trees. I have been frequently out in them skirmishing, for which they offer good cover, and have deployed in the middle of the night, and roturned at the ame time, but ever with this advantage, of not being annoyed by the onemy's fire. I find it a good half-hour's work to advance a few hundred feet, and, as for charging in line, or by separate columns, it cannot be done. In fact, the first charge we made, our troops halted at two hundred yards from the works, unablo to go further - a fact greeted by the rebels with an entire cessatiou of firing, and uproarious cheering.