The military post and academy of West Point is about fifty miles north of New York, the Government domain covering twenty-four hundred acres. The buildings stand on a plain of one hundred and sixty acres, elevated one hundred and fifty-seven feet above the river, with mountains all around, rising in some cases fifteen hundred feet, the highest being old Cro' Nest. South of the Academy, on a commanding hill six hundred feet high, are the ruins of Fort Putnam, the chief work during the Revolution. When that war began in 1775 it was ordered that the passes of the Hudson through the Highlands should be fortified, and Fort Constitution was built on the opposite island. As the higher adjacent hills commanded it, this work was soon abandoned, and three years later West Point was selected and fortified, with Fort Clinton at the Point, and several other formidable works, becoming the "American Gibraltar," the second massive chain being then extended across to the island as an additional protection. It was considered the most important post in the country, and at the time of Arnold's treason in September, 1780, was garrisoned by over three thousand men, and had one hundred and eighteen cannon in the various works. After peace came, the military defenses fell into ruin; but Washington repeatedly recommended that a military school be established at West Point, and in 1802 it was authorized by Congress, going into operation in 1812. The earthworks of the original Fort Clinton on the point, built by the youthful engineer Thaddeus Kosciusko in 1778, have been restored, and are carefully preserved. This young officer, descended from a noble Polish family, had not completed his studies in the military school of Warsaw when he eloped with a girl of high rank. The enraged father pursued and captured them, and the youthful lover was compelled either to slay the father or abandon the daughter. He chose the latter, and going to Paris met Dr. Franklin, who soon filled him with a desire to help the struggling Americans, and he came over and entered the army as an engineer in 1776. He served with distinction throughout the war, was made a General, and publicly thanked by Congress. He fought afterwards in the Polish Revolution, and retiring to Switzerland, died in 1817. He is buried in the Cathedral Church of Cracow, and near that city a mound one hundred and fifty feet high has been raised to his memory, earth being brought from every battlefield in Poland. The Kosciusko monument of marble was erected in memory of the noble Pole in an angle of Fort Clinton at West Point in 1829. ARNOLD'S TREASON.