25. Sigillaria Saullii. Coal. Manchester.

26. Sigillaria elegans. Anatomy of the stem.

27. Stigmaria ficoides. Derbyshire.

28. Transverse section of a stem of Stigmaria, showing the vascular axis. 29. Erect trunk of Sigillaria with the roots (Stigmaria) attached. Coal

36. Leaf of Zamia pectinata. Stonesfield.

37. Leaf of Pterophyllum comptum. Oolite. Scarborough. 38. Fruits of Cycadeous plants.

1. Zamia crassa. Yaverland, Isle of Wight.

40.

1. Branch of Auracaria peregrina. Lyme Regis.
2. Calamites nodosus. Coal shale.

41. Fragment of coniferous wood in flint, from the ruins of Lewes Priory. 42. Fossil fruits from the Isle of Sheppey, including the palms called

Nipatites.

43. Fossil fruits from the Isle of Sheppey, with the seed-pod of Mimosites.

44. Stems and fruit of Clathraria Lyellii. Tilgate Forest.

45. Fossil Charæ and Nymphea or water lily.

46. Fossil fruits and flower.

47. Dycotyledonous leaves.

Tertiary strata.

Tertiary strata.

CHAPTER I.

ON THE NATURE AND ARRANGEMENT OF THE BRITISH STRATA,
AND THEIR FOSSIL CONTENTS.

66 Every rock in the desert, every boulder on the plain, every pebble by the brook side, every grain of sand on the sea shore, is replete with lessons of wisdom to the mind that is fitted to receive and comprehend their sublime import."

THE solid materials of which the earth is composed, from the surface inhabited by man to the greatest depths within the reach of his observation, consist of minerals and fossils.

MINERALS are inorganic substances formed by natural operations, and are the product of chemical or electro-chemical action.

FOSSILS are the remains of animals and vegetables which have been imbedded in the strata by natural causes in remote periods; originally elaborated from inorganic matter by that marvellous principle termed vitality, and subsequently more or less altered in structure and composition by the influence of those physical forces, by which the inert substances of the mineral kingdom are subjected to perpetual change.

The soft and delicate parts of animal and vegetable organisms rapidly decompose after death; but the firmer and denser structures, such as the bones and teeth of the former, and the woody fibre of the latter, possess considerable durability, and under certain conditions will resist decay for many years, or even centuries. And when deeply imbedded in the earth, protected from atmospheric influences, and subjected to the conservative effects of various mineral solutions, the decomposition even of the most perishable tissues is often arrested, and their organization, transformed into stone, may be preserved for incalculable periods of time. Certain animal structures are even more permanent than those of vegetables, and the shells or cases of innumerable species of animalcules being composed of lime and silex or flint, are so indestructible, and occur in such inconceivable quantities, that the belief of some eminent naturalists of the last century, that every grain of flint, lime, and iron, may have been elaborated by the energies of vitality, can no longer be regarded as an extravagant hypothesis.

Some idea may be formed of the large proportion of the solid materials of our globe, which has unquestionably originated from this source, by the following list of strata, which are wholly, or in great part, composed of animal remains.

Purbeck and Sussex (Fresh-water shells, crustacea, rep- Wealden

Wealden limestone . . .

Tilgate grit (some beds) Reptiles, fishes, fresh-water shells.

1

Nor has the contribution of the vegetable kingdom to the solid crust of the earth been unimportant. Immense tracts of country are almost wholly composed of the remains of plants in the state of anthracite, coal, lignite, and brown coal; of submerged forests and peat morasses; and of layers of trees and plants transmuted into siliceous or calcareous rock.

Although these relics of animal and vegetable