XXVI

CONTENTS.

Pago

a Difference in Size—The' Holoptychius a Characteristic Ichthyo-iite of the Formation—Description of its huge Scales—Of itsOccipital Bones, Fins, Teeth, and General Appearance—Contem-poraries of the Holoptychius —Sponge-like Bodies—Plates resem-bling those of the Sturgeon—Teeth of Various Forms, but allevidently the Teeth of Fishes—Limestone Band, and its ProbableOrigin—Fossils of the Yellow Sandstone—The Pteriehthys ofDura Den—Member of a Family peculiarly Characteristic of theSystem—Vo Intervening Formation between the Old Red Sand-stone and the Coal Measures—The Holoptychius Contemporaryfora time with the Megalichthys —The Columns of Tubal Cain , 173-191

CHAPTER X.

Speculations in the Old Red Sandstone, and their Character—George, first Earl of Cromarty—His Sagacity as a Naturalist atfault in one instance—Sets himself to Dig for Coal in the LowerOld Red Sandstone—Discovers a fine Artesian 'Well—Value ofGeological Knowledge in an Economic View—Scarce a SecondaryFormation in the Kingdom in which Coal has not been sought for—Mineral Springs of the Lower Old Red Sandstone—Strathpeffer—Its Peculiarities, whence derived—Chalybeate Springs of Eas-ter Ross and the Black Isle—Petrifying Springs—Building-Stoneand Lime of the Old Red Sandstone—Its Various Soils, 192-206

CHAPTER XI.

Geological Physiognomy—Scenery of the Primary Formations;Gneiss, Mica Schist, Quartz Rock—Of the Secondary ; the ChalkFormations, the Oolite, the New Red Sandstone, the Coal Mea-sures—Scenery in the Neighbourhood of Edinburgh —Aspect ofthe Trap Rocks—The Disturbing and Denuding Agencies—Dis-tinctive Features of the 0 Id Red Sandstone—Of the Great Conglo-merate—Of the Ichthyolite Beds—The Burn of Eathie—TheUpper Old Red Sandstones—Scene in Moray, . , 207-226

CHAPTER XII.

The two Aspects in which Matter can be Viewed : Space and Time—Geological History of the Earlier Periods—The Cambrian Sys-tem—Its Annelids—TheSilurian System—Its Corals, Encrinites,Molluscs , and Trilobites—Its Fish—These of a High Order, andcalled into Existence apparently by Myriads—Opening Scene inthe History of the Old Red Sandstone a Scene of Tempest—Re-presented by the Great Conglomerate—Red a prevailing Colour