BOOK VI

TREATING OF EARTHQUAKES

CHAP. PAGE

I. Earthquake at Pompeii and the alarm it caused, many giving up Campania as a residence altogether. If the solid earth fail, what can be done? Refuge from tempest and fire and thunderstorm and war is possible, but not from earthquake. But (1) the whole earth is subject to such movement: we cannot escape by changing our ground--Tyre, Asia Minor, Achaia have all suffered. (2) Death is the same in whatever form it come, the circumstances matter not, a stone is all one with a mountain 221

II. We cannot escape death. The hopeless find refuge in despair. The knowledge of our frailty and mortality is our true solace. Death must come, a death with circumstance is rather to be preferred than otherwise. In an earthquake the earth shows itself mortal as men are 225

III. Our fears are due to ignorance. Through lack of a philosophic view of the universe we consider phenomena strange which are merely rare, _e.g._ eclipses. Fear may be removed by knowledge 228

IV. The study of such problems is the very worthiest; it reveals the secrets of nature, and is disinterested. But it is highly profitable at the same time 229

V. Various explanations of _earthquakes_ have been suggested. The earlier ones are crude, but not therefore to be despised. Every subject develops as time goes on. Gratitude is due to the investigators who first dared to question nature 230

VI. The cause of earthquakes is by some said to be water. Thales of Miletus explains how this takes place, but he must be wrong: the analogy of a ship sailing the ocean will not apply to the earth (cp. III. xiii.) 231

VII. Water may be the cause, but may operate in quite different ways from those supposed by Thales. Storms, etc., in subterranean seas may cause earthquakes 233

VIII. There must be such subterranean water. The Tigris and Arethusa prove it. Nero, the virtuous and the veracious, sent two officers to investigate the sources of the Nile; their account confirms the assumption 235

IX. Fire is another alleged cause. It either bursts out through opposing obstacles, as in the clouds (Anaxagoras), or burns away the foundation and causes a subsidence at the spot 236

X. Pieces of the earth falling in merely through the decay of age may produce the effect without fire or any external influence. This is Anaximenes’ opinion 237

XI. Fire is supposed by some to cause earthquakes by expanding the vapour which it first causes to be given off from the subterranean waters 238

XII. Archelaus sets down the cause as air pressing up the earth’s internal wind which is already condensed to bursting point 239

XIII. Aristotle and Theophrastus take evaporation to be the cause. Strato, much in the same way, thinks that differences of internal temperature are the cause 240

XIV. By some it is thought that air is the cause, but that its operation, along with water, is like that of blood and air in the vessels of the body. The earth, it is assumed in this case, admits air, which must find an exit. When it does so violently, the result is an earthquake 242

XV. The earth is porous, perforated at many points, and it is thus that the air enters 243

XVI. The earth is full of air, nourishing plants rooted in it, and exhaling enough to feed the sun and the other heavenly bodies. Air is the most movable of elements; therefore the earth, if it is full of air, must also have frequent movements 244

XVII. Obstruction of air, just as of water, causes greater impetuosity when it escapes. Wind is frequently associated with earthquakes, as at Chalcis 245

XVIII. Additional considerations to prove that the great cause of earthquakes is air, _i.e._ wind 247

XIX. Metrodorus of Chios compares the rumbling of an earthquake to the resonance of the voice in a tub; the underground caves impart the sound 248

XX. Various combinations of water and air supposed by Democritus and Epicurus to co-operate to the production of earthquakes 249

XXI. Air must be the cause. Different kinds of earthquakes 251

XXII. First species--shaking of the earth: its causes 252

XXIII. Next comes the form of concussion caused by air. The great Callisthenes, who braved the fury of Alexander and lost his life for it, supports this view. Submarine effects of it are particularly noticeable 253

XXIV. Different explanations may be given of the exact method in which air acts 255

XXV. The striving of the air in subterranean caverns produces a concussion or collapse in the earth above. The area of disturbance is limited, never over 200 miles, as numerous instances prove. The Peneüs and Ladon were thus produced 256

XXVI. The nature of the soil composed of muddy accretions without interstices is said to account for the exemption of Egypt from earthquakes. So Delos in the sea has porous rocks which emit the air easily. But the facts are wrong. There is abundant proof that proximity to the sea is no safeguard against shock 258

XXVII. A peculiarity of the Campanian earthquake, that it killed 600 sheep, is explained by the emission of pestilential vapour, by which sheep, with their heads close to the ground, naturally were most readily affected 259

XXVIII. Noxious vapours are not, however, peculiar to earthquakes. They are found in several parts of Italy habitually. Such, too, is the origin of new diseases 261

XXIX. Excessive fear drives people mad. Earthquakes split statues and divide kingdoms, _e.g._ Sicily from Italy, Spain from Africa 262

XXX. The action of the air accounts for all the detailed phenomena, splitting of walls, houses, towers, statues; also for the prolongation of shocks for several days 263

XXXI. A further proof that air is the agent is to be found in the gradually diminishing violence of the successive shocks. Phenomena in the pavement witnessed by a philosopher who was in his bath 264

XXXII. The moral. Life hangs on a thread; why should one dread the loss of it? The greatness of the cause of death is no source of terror. The hereafter is better and safer than earth. There there is no fear of earthquake or thunderstorm, fire or flood. Fear of death magnifies all human risks. Do not dread death, long for it, and, if necessary, meet it half way 265