The men of antiquity conceived of the interaction of atmosphere and earth in two ways: effects produced by the land upon the atmosphere, and effects produced by the winds upon the land. In connection with the first, Seneca makes a remark which, when taken from its context, would not be out of place in a modern manual of meteorology. He conceived the lower portion of the atmosphere to be extremely variable and inconstant as a result of the proximity of the earth. “The earth is a more important cause than all others ... for the air’s changefulness and inconstancy. The varying positions of the land, facing here this way and there another way, are of great moment in determining the temperature of the air.”[75] Nothing is truer than this, but the reasons that Seneca gives for the influence of the atmosphere upon the land are not satisfactory, being based to a large extent on the supposition that winds are produced by vapors. Indeed, by the theory of vapors and exhalations many ancient and medieval thinkers attempted to explain nearly all the phenomena of the atmosphere and heavens as well. Aristotle had pointed out that a dry and smokelike exhalation is caused by the sun to rise from the earth’s surface through the air and even to penetrate the zone of fire.[76] While near the earth this exhalation takes the form of wind; when ignited at higher levels it becomes comets and shooting stars. Besides this, Aristotle maintained that a damp and watery vapor is also drawn into the atmosphere by the sun’s heat and when cooled turns into cloud or falls in the form of rain and snow.[77] These ideas of Aristotle became known to the Western world of the Middle Ages with translations of the _De caelo_ and _Meteorology_ and found their expression in the thirteenth-century writings of Albertus Magnus.[78] Seneca, on the other hand, explained that the winds were air in motion and that they might be produced by many and various causes.[79] WINDS All three of the writers whom we are specially considering,[80] Aristotle, Seneca, and Pliny, had observed that there is a variety of local winds—valley, river, sea, and marsh breezes—taking their origin from the exhalations and vapors arising from these natural features. But even though their explanations of the causes for these winds are now regarded as archaic, the observations they made of their occurrence were not inaccurate. As to the effects of the winds on the earth, we encounter a theory that sounds most extraordinary in the light of modern science but which corresponds logically to the Aristotelian hypothesis of the elements and to the general ideas current in classical times regarding the structure of the earth. This theory, that the winds are the cause of earthquakes, can better be understood after we have examined the ancient opinions about the physical geography of the water and of the earth.