In the absence of any real history of Ireland, the memoirs of its distinguished persons are of the first importance. They are the landmarks within which the broad and general track of historic narrative must be led. They fix character--the most necessary aid to the larger views of the historian. They disclose to us those secret springs which regulate the great social machinery; and by an especial faculty, more valuable than all, they bring us face to face with minds of acknowledged eminence, teach us the course which the known conquerors of difficulties have pursued, and exhibit the training by which the championship of nations is to be sustained. As the old lawgiver commanded that beautiful statues should be placed before the Spartan wives, to impress their infants with beauty of countenance and stateliness of form, the study of greatness has a tendency to elevate our nature; and though camps and councils may be above our course, yet the light shed from those higher spheres may guide our steps through the tangled paths of our humbler world. The present memoir gives evidence of an additional merit in biography: it assists justice; it offers the power of clearing character, which might have been refused to the living; it brings forward means of justification, which the dignity of the injured, his contempt of calumny, or the circumstances of his time, might have locked up in his bosom. It is an appeal from the passion of the hour to the soberness of years. It has the sincerity and the sanctity of a voice from the world of the future. The Stewarts, ancestors of the Marquis of Londonderry, came originally from Scotland, and, settling in Ireland in the reign of James I., obtained large possessions among the forfeited lands in Ulster. The family were Protestants, and distinguished themselves by Protestant loyalty in the troubled times of Ireland--a country where trouble seems to be indigenous. One of those loyalists was Colonel William Stewart, who, during the Irish war, under James II., raised a troop of horse at his own expense, and skirmished vigorously against the Popish enemy at the siege of Londonderry. For this good service he was attainted, with all the chief gentry of the kingdom, in the confiscating parliament of James. But the confiscation was not carried into effect, and the estate remained to a long line of successors.