Since the period when the white chalk which now forms our cliffs and hills was deposited at the bottom of a vast and deep ocean--the sea bottom has been raised, the chalk has emerged and risen on the top of hills to 800 feet in height in our own islands, and to ten times that height elsewhere, and during that process sands and clays and shelly gravels have been deposited to the thickness of some 2,800 feet by seas and estuaries and lakes, which have come and gone on the face of Europe and of other parts of the world as it has slowly sunk and slowly risen again. The last 200 feet or so of deposits we call the Pleistocene or Quaternary; the rest are known as the Tertiary strata. They are only a small part of the total thickness of aqueous deposit of stratified rock--which amounts to 60,000 feet more before the earliest remains of life in the Cambrian beds are reached, whilst older than, and therefore below this, we have another 50,000 feet of water-made rock which yields no fossils--no remains of living things, though living things were certainly there! Our little layer of Tertiary strata on the top is, however, very important. It took several million years in forming, although it is only one-fortieth of the whole thickness of aqueous deposit on the crust of the earth. We divide it into Pliocene, Miocene, and Eocene, and each of these into upper, middle, and lower, the Eocene being the oldest. Our London clay and Woolwich sands are lower Eocene; there is a good deal of Miocene in Switzerland and Germany, whilst the Pliocene is represented by whole provinces of Italy, parts of central France, and by the White and Red "crags" of Suffolk.[5] [Illustration: Fig. 9.--Skeleton of the Indian elephant. Only four toes are visible, the fifth concealed owing to the view from the side.]