The opinions of various philosophers on comets are quoted and criticised. He is especially severe in his comments on Epigenes, who thought that comets are produced somewhat as fires are excited by whirlwinds. The Greek threefold classification of comets is cited, and then Artemidorus comes in for his share of vituperation; to disprove his theory of the firmament being a solid roof to the world would be, in the author’s opinion, nothing but beating the air. Ephorus fares no better, being briefly dismissed as often deceiving and often deceived. Apollonius of Myndus held that many comets are distinct planetary bodies, which wax and wane like the planets, being brightest when they are nearest us and growing dimmer as they recede to a greater distance. But Seneca refuses to admit that they have the character of true planets; in his view they are insubstantial irregular fire (291). But he does not agree with his Stoic brethren in regarding them as generated in dense air and pursuing their course according to where they can find fuel to sustain them (292–4). He conceives that they are not mere sudden and transient fires, but belong to the eternal works of nature. They steadily traverse their course, and he can understand that they may have such wide orbits as to carry them far beyond the limits of the Zodiac (296). He can see no reason why the five planets then known should be the only stars that move across the sky, though others had not yet been discovered. Astronomy, he remarks, is in its infancy, many mysteries of nature remain still to be discovered, and the day will come when posterity will marvel at our ignorance of things which will then appear to be so evident. Some future observer will demonstrate the paths of the comets, why they wander so far from the other stars, and what is their size and constitution. We may be content with what we have found out, and leave something for posterity to discover. In a tone of sad pessimism he brings his volume to a close. From a contemplation of the glories that might be achieved by mankind in searching out the marvels of creation he turns to his own age and his own country, only to see on every side proofs of decadence. No one now cared for the pursuit of wisdom. Philosophy and every liberal study were neglected. The schools of philosophy were dying. If his countrymen even now would set themselves with all their energy to the task, if the young would give their sober attention and the elders would teach them, they would scarcely succeed in reaching the bottom of the well in which truth lies. Meanwhile they were searching merely on the surface of the ground and with but a slack hand. NOTES BY TRANSLATOR “AIR”