Many of the greatest authorities are persuaded that earthquakes are 1 to be attributed to air. Archelaus, who is well versed in the records of antiquity, speaks thus: Winds are carried down into the earth’s hollows and recesses. When they are all full, and the atmosphere is condensed to the utmost extent, the air, which continues to come in, forces and thrusts the former air, and with frequent blows first compresses and then dislodges it. The air in its endeavour to find 2 room forces all the narrow passages and tries to burst its barriers. Through the struggle of the air as it seeks for an escape it comes to pass that the earth is moved. This explains why the approach of an earthquake is preceded by still and quiet of the atmosphere; the force of the air which is wont to rouse the winds is held in check in its nether abode. Even on the present occasion of the earthquake in 3 Campania, although the season was winter, the atmosphere was perfectly still and calm for several days before it.[81] Well, then, did an earthquake never take place when there was a wind blowing? On very rare occasions have there been two winds blowing simultaneously. Still, such a thing is possible, and is wont to occur. But if we admit it as an established fact that two winds can be in activity at one and the same time, why shouldn’t it happen that [at times] one of them agitates the upper air, the other the nether?[82] [81] The text is uncertain, and the argument down to the end of the chapter rather obscure. [82] The argument seems to be: Two winds can blow simultaneously. One may be beneath the earth (causing or during earthquake), one above. Therefore, stillness of the upper atmosphere is not a necessary concomitant of earthquake. The fact has at times been otherwise. XIII