To obtain knowledge we must exercise the perceptive faculties. The senses of seeing, hearing, smelling, tasting and touching are the only avenues by which knowledge can reach the mind. He whose observation has been the most comprehensive, and whose investigations have been the most thorough and accurate, is enabled to exercise the contemplative powers with the greatest pleasure and advantage. The distinct and graphic imagery of men, scenes, events, objects and their properties, with which he has stored his mind, will give correctness to his ideas, variety to his mental operations, comprehensiveness to his intellectual view, clearness to his judgment, and truth to his conclusions. Possessing the elements of correctness, he will also possess the elements of happiness and success. He is enabled to open the volume of Nature, and read, in her pages of rocks and stars, sublimer periods than the pen of superstition ever recorded. He stands perpetually in the vestibule of truth, opening on the fields of immensity, strewed with objects of reality, before the blaze of whose overpowering grandeur the throne and empire of fancy dwindle into insignificance. He is enabled to imbibe the fervor, inhale the inspiration, and enjoy the ecstatic delights which scientific truth alone can confer, and which in intensity and purity so far transcend the fanatic's wildest excitement. He is inducted into the secret by which science has achieved all her victories, and by which she has erected in such solid grace and grandeur those literary and philosophical structures which stand like imperishable columns amid the ruin of temples and kingdoms.