The cause of earthquakes has been assigned variously by different 1 authorities to water, fire, air, and to the earth itself; some assign it to a combination of several of the causes, others, to a union of them all. Certain writers have stated that it was plain to them that some one of these causes produced the earthquake, but it was not plain which. Let us look at the various opinions in detail. First of all, I feel bound to say in general terms that the old views are crude and inexact. As yet men were groping their way round truth. Everything was new to those who made the first attempt to grasp it; only later were the subjects accurately investigated. But all subsequent discoveries must nonetheless be set down to the credit of those early thinkers. It was a task demanding great courage to remove the veil that hid 2 nature, and, not satisfied with a superficial view, to look beneath the surface and dive into the secrets of the gods. A great contribution to discovery was made by the man who first conceived the hope of its possibility. We must, therefore, listen indulgently to the ancients. No subject is perfected while it is but beginning. The truth holds not merely of the subject we are dealing with, the greatest and most complicated of all, in which, however much may be accomplished, every succeeding age will still find something fresh to accomplish. It holds alike in every other concern; the first principles have always been a long way off from the completed science. VI Water is the first cause alleged: more authors than one adopt this 1 view, but it is not stated by all in the same terms. Thales of Miletus is convinced that the whole earth floats, and is upborne by moisture lying beneath it, which you may call either Ocean or the great sea, or still mere elemental water of a different character from the sea, the simple ingredient, moisture. In these waves, in his opinion, the globe is supported like some huge lumbering vessel in the water which bears it. It is unnecessary for me to reproduce his reasons for supposing 2 that the heaviest part of the world cannot be sustained in such a rare and nimble element as air: for the earth’s position is not the question here but its movement. By way of argument, to prove that water is the cause, he adduces the fact that in every considerable earthquake, as a rule, new springs burst out. So if a boat leans over to one side away from the straight, the result is that it ships water. And, generally speaking, in the case of all objects which water supports, if they are unduly sunk, the water either pours over them or at any rate rises to right and left above its ordinary height.