VI. Arguments from the size--never more than a semicircle--and shape of the bow. As the colour, whether real or reflected, is derived from the sun, so must also the shape be. The size is accounted for by the magnifying power of water, glass, etc. The sun as he appears in the rainbow is seen through moisture 28 VII. The arguments from the dispersion of the sun’s rays through glass (prism). Contention that they confirm author’s view 30 VIII. The form once more; why it is never larger than a semicircle. A wrong explanation refuted. Explanation of Aristotle’s remark as to the seasons of rainbows, in summer only in the morning or evening, in autumn at any time 31 IX. _Streaks_ or _weather-galls_. Merely abortive or imperfect rainbows 33 X. Relations and differences of _halos_, _bows_, and _weather-galls_ 34 XI. _Mock suns._ Their appearance and position in relation to the sun. They are a reflection of the sun in a suitable medium 34 XII. The formation of a mock sun may be compared to the image of the sun in eclipse as seen reflected in a dish of oil or pitch: the medium must be adapted to give the impression. The mock sun requires a certain consistency of cloud, failing which, a different effect is produced--obscuration, dissipation, etc. 35 XIII. There may be two mock suns simultaneously. Some think the one is a reflection of the other, the clouds acting as mirrors set opposite to one another. Mock suns, especially in the South, are a sign of rain 36 XIV. Other celestial fires. “_Cave meteors_,” “_Barrel meteors_,” “_Chasms_,” with a brief description of each. The rapidity of their flight, just as of lightning, deceives the sight. Their origin and cause. They indicate wind 37 XV. _Gleams_ (_flashes_, σέλα). Their production and motions, varieties of them. Some do damage. Some are analogous to comets. “_Bearded_,” “_torches_,” “_cypress_” are different kinds. “_Beams_” and “_barrels_” may be of the same class. A curious case where such an appearance raised an alarm of fire. They are real fires. On the contrary, rainbows and halos are mere reflections. Mirrors have this wonderful power of false presentation 39 XVI. The “mirrored den” of Hostius Quadra 41