Influence of the Forest, considered as Inorganic Matter, on Temperature: _a_, Absorbing and Emitting Surface; _b_, Trees as Conductors of Heat; _c_, Trees in Summer and in Winter; _d_, Dead Products of Tree; _e_, Trees as a Shelter to Grounds to the leeward of them; _f_, Trees as a Protection against Malaria--The Forest, as Inorganic Matter, tends to mitigate extremes. Trees as Organisms: Specific Temperature--Total Influence of the Forest on Temperature. Influence of Forests on the Humidity of the Air and the Earth: _a_, as Inorganic Matter; _b_, as Organic--Wood Mosses and Fungi--Flow of Sap--Absorption and Exhalation of Moisture by Trees--Balance of Conflicting Influences--Influence of the Forest on Temperature and Precipitation--Influence of the Forest on the Humidity of the Soil--Its Influence on the Flow of Springs--General Consequences of the Destruction of the Woods--Literature and Condition of the Forest in different Countries--The Influence of the Forest on Inundations-- Destructive Action of Torrents--The Po and its Deposits-- Mountain Slides--Protection against the Fall of Rocks and Avalanches by Trees--Principal Causes of the Destruction of the Forest--American Forest Trees--Special Causes of the Destruction of European Woods--Royal Forests and Game Laws-- Small Forest Plants, Vitality of Seeds--Utility of the Forest--The Forests of Europe--Forests of the United States and Canada--The Economy of the Forest--European and American Trees Compared--Sylviculture--Instability of American Life, 128 CHAPTER IV. THE WATERS. Land artificially won from the Waters: _a_, Exclusion of the Sea by Diking; _b_, Draining of Lakes and Marshes; _c_, Geographical Influence of such Operations--Lowering of Lakes--Mountain Lakes-- Climatic Effects of Draining Lakes and Marshes. Geographical and Climatic Effects of Aqueducts, Reservoirs, and Canals--Surface and Underdraining, and their Climatic and Geographical Effects--Irrigation and its Climatic and Geographical Effects. Inundations and Torrents: _a_, River Embankments; _b_, Floods of the Ardeche; _c_, Crushing Force of Torrents; _d_, Inundations of 1856 in France; _e_, Remedies against Inundations--Consequences if the Nile had been confined by Lateral Dikes. Improvements in the Val di Chiana--Improvements in the Tuscan Maremme--Obstruction of River Mouths--Subterranean Waters-- Artesian Wells--Artificial Springs--Economizing Precipitation, 330 CHAPTER V. THE SANDS.