It is not difficult to realise how this explanation should have been accepted in antiquity, and should have held its ground down even into modern times. The violence of the commotions of the atmosphere was a familiar feature on the surface of the earth, although its physical causes, variously guessed at, were utterly unknown. To minds that had no conception of the very rudiments of meteorology, there seemed to be no reason why air inside the earth should not be affected by as violent hurricanes as the air outside. And as such hurricanes were the most powerful natural agencies known, their action was not unreasonably invoked to account for the phenomena of earthquakes. Assuming that the air in a large subterranean cavern would behave as the free open atmosphere does, the old philosophers did not find themselves under the necessity of explaining what was to set the air in motion within the subterranean recesses and lash it into fury there, any more than they had to account for tempests above ground. Obviously, if the air found its way from the outside into the internal parts of the earth, it must have had equal facilities for egress. And in the convulsions of an earthquake it might be supposed to issue with violence through some of the previous openings or from the rents made at the time. In corroboration of the truth of the prevalent opinion, it was asserted that after an earthquake air was found to issue from the ground, but no account appears to have been preserved of any violent outrush of air. As a further evidence that it is to the force of air that all these internal disturbances are due, the author remarks that after a violent earthquake another shock of equal violence cannot occur, because the first has opened a passage for the struggling winds. The progress of investigation has, in modern times, thrown a flood of light on the phenomena of earthquakes, though there still remain many problems in the subject which await solution. It is needless to say that no foundation whatever has been found for the ancient faith that the air plays the chief part in these subterranean commotions.