XVI. Intermittent fountains are an illustration of seasonal activity. The great vacant spaces of the earth and their tenants. Underground fish 128 XVII. The incredible wonders of nature are paralleled and even outdone by the excesses of luxury 129 XVIII. The extravagances of luxury, which make a wise man mad 130 XIX. To return--a sudden eruption of water casts up fish, generally poisonous. This points to the unfailing supply of subterranean water 132 XX. Various tastes of water due to four causes; qualities of water--petrifying, soporific, intoxicating, fatal 133 XXI. The same pestilential influence as taints rivers is perceived in caves: the noxious rivers flow from or through them 134 XXII. The Ocean and seas are coeval with the universe. So probably are abnormal rivers like the Danube and the Nile 135 XXIII. Rain and surface water must be added to subterranean 135 XXIV. The causes of hot springs 136 XXV. Poisonous rivers. Colouring power of others. Great specific gravity of certain waters, its effects and cause 137 XXVI. Intermittent rivers and springs. Means possessed by river, fount, and sea of purifying themselves 141 XXVII. Digression on the universal deluge which will destroy the world. Nature is niggardly in creation, lavish in destruction. Ovid is unequal in his treatment of this catastrophe 143 XXVIII. Further imaginative pictures of what water can do by way of destruction. Alternative methods of destroying the earth--water and fire 148 XXIX. Further possibilities of the same character. Distinctions of seas, gulfs, etc., will all be obliterated; nature and the works of man will alike be overthrown 150 XXX. Nature shows by the chafing of the sea that she designs to inundate the world. A deluge is part of the fore-ordained plan. But there will be a new earth and a new race of men who will not sin--for a time 154 BOOK IV CONTAINING A DISCUSSION OF SNOW, HAIL, AND RAIN. [THE NILE] PREFACE The dangers of flattery and its insidiousness. If you must have praise, praise yourself. Lucilius has good cause: he must not, however, think too much of himself because he is governor of that historic province Sicily, which has ere now decided the fate of generals and of empire 159