Sackville Street is a splendid business avenue leading from Carlisle Bridge. It is full one hundred feet wide, and filled with a hurrying, Broadway or Washington Street-like population. On the left stands the classical portico of the post-office, composed of six large Ionic columns, and their entablature and pediment. It is surmounted by figures of Hibernia, Mercury, and Fidelity. In front, at the centre of the street, is Nelson's monument, a splendid column 112 feet high,--exclusive of the crowning statue of the hero of Trafalgar, which is in itself 13 feet in height. This is a fine piece of sculpture, and is from the studio of a native sculptor, Thomas Kirk. The monument was erected by public subscription and cost over $34,000. In consequence of the general levelness of the city of Dublin, from the top of this column, though not of very great height, may be seen almost the entire surrounding country, from the Mourne Mountains in the county of Down on the north, around to the Wicklow Mountains on the south. Spread out before the observer are the plains of Meath and Kildare, extending far westward, and parted by the hills of Dublin and its bay; and to the eastward appears the Irish Sea. The Custom House and the Four Courts of Dublin are immense structures, of classical architecture, and well decorated with statuary. On the former are statues representing Navigation, Wealth, Commerce, Industry, Europe, Asia, America, and Africa. Other parts have the arms of Ireland. There is a fine allegorical representation of Britannia and Hibernia in a great marine shell, with a group of merchantmen approaching, and Neptune driving away Famine and Despair. The Court House has on the upper angle of its great portico pediment a statue of Moses, and at the lower ends statues of Mercy and Justice. On other parts are Wisdom and Authority. The great entrance hall is 64 feet in diameter; at the centre stands a colossal statue of Truth, bearing in her upraised hand a torch, from which issue gas jets for illuminating the rotunda. We attended a court session. The rooms were cramped in size, and dark from the few smoked and unwashed windows. A peculiar impression was made, reminding us of a by-gone custom and age, when we saw the lawyers,--or barristers as they are called,--old and young, arrayed in loose black alpaca robes, open in front and flying as they walk, and wearing gray wigs of scrupulously curled hair. These are for sale in especial stores, and their use is imperative when one addresses the judge of any save the lowest common police court.