IV 



CONTENTS. 



CHAPTER XIV. 



AGENTS WHICH DESTROY ROCKS (CONTINUED). 



Destruction of the Land in Boston Harbour. — Chemical Action. 

 — Causes which hasten it. — Destruction of Rocks proved by 

 the Nature of the Soil. — Granite Soil. — Gneiss Soil.— Slate 

 Soil. — Limestone Soil.— Soil of Red Sandstone Regions. — 

 Freezing and Thawing. — Moving of Rocks by the Expansion 

 of Ice. — Lightning. — Falling of Glaciers . . Page 143 



CHAPTER XV. l 



AGENTS WHICH FORM ROCKS. 



Quantity of Sediment in River-water. — In the Rhine— In the 

 bellow River. — In the Ganges.— Deltas. — Delta in the Lake 

 of Geneva — Lake Mareotis — North American Lakes.— Delta 

 of Inland Seas— Of the Rhone— Of the Po— Of the Nile— Of 

 the Ganges — The Mississippi 154 



CHAPTER XVI. 



AGENTS WHICH FORM ROCKS (CONTINUED). 



Agents which form Rocks. — Coral Animalcules. — Coral Reefs : 

 how formed. — General Form. — Submarine Volcanoes. — Basil 

 Hall's description of Loo Choo.— Montgomery's poetical De- 

 scription .168 



CHAPTER XVII. 



AGENTS WHICH FORM ROCKS (CONTINUED). 



Springs. 



Springs, how supplied.— Artesian Wells. — Mineral and Ther- 

 mal Springs. — Calcareous Springs. — Travertin. — Silicious 

 Springs. — Geysers of Iceland. — Sinter.— Hot Springs of St. 

 Michael. — Silicious Deposites. — Ferruginous Springs. — Nap- 

 tha and Asphaltum Springs. — Pitch Lake of Trmidad . 175 



CHAPTER XVIII. 



AGENTS WHICH FORM ROCKS (CONTINUED). 



Igneous Causes. 



Volcanic Action. — Definition.— Leibnitz's Theory. — Charles 

 Darwin's Hypothesis.— Sir Humphrey Davy's Hypothesis. — 

 Phenomena of Volcanic Eruptions.— Quantity of Ejected Mat- 

 ter.— Skaptar Jokul in Iceland. — Tomboro. — Submarine Vol- 

 canoes.— Graham Island.— Etna. — Vesuvius — Pompeii.— 

 Herculaneum.— Earthquakes 186 



