When a man has reached middle-age he generally feels with tenfold force the truth of those "sayings of the wise" which he learned in his early years, and has cause to regret, as well as wonder, that he had not all along followed their wholesome teaching. For it is to the young, who are about to cross the threshold of active life, that such terse convincing sentences are more especially addressed, and, spite of the proverbial heedlessness of youth,...