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. 
AGENTS WHICH FORM ROCKS. 
Quantity of Sediment in River-water.— In the Rhine— In the 
Vellow 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 XVL 
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 XVIL 
AGENTS WHICH FORM ROCKS (CONTINOBD). 
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 Trinidad . 175 
CHAPTER XVm. 
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 
