“Time writes no wrinkle on thine azure brow; Such as creation’s dawn beheld, thou rollest now!” No one can write the history of the Chalk formation, without remembering his indebtedness to the patient and laborious toil of Dr. Mantell in this department, from whose “Geological Excursions round the Isle of Wight,”[104] we give the following extract. “The features of a chalk district are so well known, that a brief notice will render local details unnecessary. The rounded summits of the hills, covered with short verdant turf—the smooth undulated outline of the downs unbroken, save by the sepulchral mounds of the early inhabitants of the country—the coombes and furrows ramifying and extending into the deep valleys, which abruptly terminate at the base of the hills, and appear like dried-up channels of rivulets and streams, though free from all traces of alluvial débris, thus bearing the impress of physical operations, of which the agents that produced them have long since passed away—are phenomena familiar to every one who has travelled over the downs of the south-east of England, and are displayed in the chalk districts of the ‘beautiful isle.’ These features are restricted to the hilly districts of the _white chalk_, and have resulted from the peculiar nature of the sedimentary detritus,[105] of which the strata comprised in the upper division of the Cretaceous system are composed: for in the lower groups, clays, marls, sands, and sandstones prevail; and where these deposits approach the surface, and form the subsoil, the country is broken and diversified, and the landscape presents a striking contrast with the down scenery, as may be observed in the picturesque district which flanks the escarpment of the chalk hills. It may, perhaps, be necessary to remind the unscientific reader, that these strata are but an insulated portion of an ancient sea-bottom, or in other words, a mass of consolidated sediments formed in the profound depths of the ocean, in a very remote period of the earth’s physical history. This detritus is made up of inorganic and organic materials. The former consist of the débris of the cliffs and shores which encompassed the ancient sea, of the spoils of islands and continents brought down into the ocean by fresh-water currents, and of chemical deposits thrown down from mineral solutions. The organic substances are the durable remains of animals and plants which lived and died in the ocean, and of fluviatile and terrestrial species that were transported from the land by rivers and their tributaries; the whole forming such an assemblage of sedimentary deposits as would probably be presented to observation, if a _mass of the bed of the Atlantic ocean_, 2,000 feet in thickness, were elevated above the waters, and became dry land.”