_The Duty of acquiring Knowledge._--In starting the discussion of any particular set of duties, it is advisable, as has been said, to present some concrete case, and biographical or historical examples are particularly useful. I have sometimes begun the lesson on the duty of acquiring knowledge by telling the story of Cleanthes and that of Hillel. Cleanthes, a poor boy, was anxious to attend the school of Zeno. But he was compelled to work for his bread, and could not spend his days in study as he longed to do. He was, however, so eager to learn that he found a way of doing his work by night. He helped a gardener to water his plants, and also engaged to grind corn on a hand-mill for a certain woman. Now the neighbors, who knew that he was poor, and who never saw him go to work, were puzzled to think how he obtained the means to live. They suspected him of stealing, and he was called before the Judge to explain. The Judge addressed him severely, and commanded him to tell the truth. Cleanthes requested that the gardener and the woman might be sent for, and they testified that he had been in the habit of working for them by night. The Judge was touched by his great zeal for knowledge, acquitted him of the charge, and offered him a gift of money. But Zeno would not permit him to take the gift. Cleanthes became the best pupil of Zeno, and grew up to be a very wise and learned man, indeed one of the most famous philosophers of the Stoic school. The story of Hillel runs as follows: There was once a poor lad named Hillel. His parents were dead, and he had neither relatives nor friends. He was anxious to go to school, but, though he worked hard, he did not earn enough to pay the tuition fee exacted at the door. So he decided to save money by spending only half his earnings for food. He ate little, and that little was of poor quality, but he was perfectly happy, because with what he laid aside he could now pay the door-keeper and find a place inside, where he might listen and learn. This he did for some time, but one day he was so unlucky as to lose his situation. He had now no money left to buy bread, but he hardly thought of that, so much was he grieved at the thought that he should never get back to his beloved school. He begged the door-keeper to let him in, but the surly man refused to do so. In his despair a happy thought occurred to him. He had noticed a skylight on the roof. He climbed up to this, and to his delight found that through a crack he could hear all that was said inside. So he sat there and listened, and did not notice that evening was coming on, and that the snow was beginning to fall. Next morning when the teachers and pupils assembled as usual, every one remarked how dark the room seemed. The sun too was shining again by this time quite brightly outside. Suddenly some one happened to look up and with an exclamation of surprise pointed out the figure of a boy against the skylight. Quickly