The story abruptly ends here, for Plato left no further record. CHAPTER XXXIX NATURE'S WARNING OF COMING EARTHQUAKES That there are signs of coming earthquakes which might be read by man, had he sufficient knowledge, there would seem to be but little doubt. These phenomena follow natural laws so that the approach of an earthquake must necessarily be in a definite order both as regards the phenomena which precede as well as those which follow it. There should, therefore, be signs that would enable one to predict its coming, although it must be acknowledged that these signs, so far as we actually know, are indistinct. It may seem to the unthinking and unobservant that the awful catastrophe of an earthquake comes entirely unheralded; that, apparently, it is not until the earth's surface begins to rock to and fro under the mighty forces that are causing destruction that its presence can be known. There are, however, many reasons for believing that in, perhaps, the greatest number of cases, it might have been foreseen, if greater attention had been given to the slight indications of its probable approach a short time before its occurrence. It is evident that the conditions of great pressure or stress in the earth's crust which finally result in a disastrous earthquake have been slowly accumulating for a long time, and that when the pressure at last reaches a point where the crust has to yield or slip, the ground is suddenly crushed and tossed to and fro while vast fissures and chasms are produced in the subterranean regions. At those points of the earth immediately above or in the neighborhood of such regions it is possible that there are many signs of the coming quake; and, although indistinguishable by our duller senses, are readily appreciated by the more highly developed senses of the lower animals. Indeed, had we accustomed ourselves to reading the various indications of nature as the lower animals have, we, too, might be able to read these warnings of the coming earthquake. At great distances from the place where the earthquake starts there would necessarily be a better opportunity for predicting its approach. As already stated, what is called an earthquake does not consist of a single shaking of the ground, but of a highly complex series of shakings. According to Mallet, the following waves start at the same time from the place of origin of an earthquake, when located on the bed of an ocean; i. e., an earth sound wave and a earth wave constituting the earth's shake; a sound wave through the ocean, another through the air; a sea wave called by him a forced sea wave, and finally the great sea wave.