The building of Dublin "Castle"--for the residence of the Viceroys retains the term--was commenced by Meiler FitzHenry, Lord Justice of Ireland, in 1205; and finished, fifteen years afterward, by Henry de Loundres, Archbishop of Dublin. The purpose of the structure is declared by the patent by which King John commanded its erection: "You have given us to understand that you have not a convenient place wherein our treasure may be safely deposited; and forasmuch, as well for that use as for many others, a fortress would be necessary for us at Dublin, we command you to erect a castle there, in such competent place as you shall judge most expedient, as well to curb the city as to defend it if occasion shall so require, and that you make it as strong as you can with good and durable walls." Accordingly it was occupied as a strong fortress only, until the reign of Elizabeth, when it became the seat of the Irish government--the court being held previously at various palaces in the city or its suburbs; and in the seventeenth century, Terms and Parliaments were both held within its walls. The Castle, however, has undergone so many and such various changes from time to time, as circumstances justified the withdrawal of its defenses, that the only portion of it which nows bears a character of antiquity is the Birmingham Tower; and even that has been almost entirely rebuilt, altho it retains its ancient form. The records of this tower--in modern times the "State Paper Office"--would afford materials for one of the most singular and romantic histories ever published. It received its name, according to Dr. Walsh, not from the De Birminghams, who were lords justices in 1321 and 1348; but from Sir William Birmingham, who was imprisioned there in 1331, with his son Walter; "the former was taken out from thence and executed, the latter was pardoned as to life because he was in holy orders." It was the ancient keep, or ballium, of the fortress; and was for a very long period the great state prison, in which were confined the resolute or obstinate Milesian chiefs, and the rebellious Anglo-Norman lords. Strong and well guarded as it was, however, its inmates contrived occasionally to escape from its durance. Some of the escapes which the historians have recorded are remarkable and interesting.