GEOLOGICAL STRATA SINCE THE CHALK 135 



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 ft 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 

 2800 ft. 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 ft. 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 ft. more before the earliest remains of life in the 

 Cambrian beds are reached, whilst older than, and therefore 

 below this, we have another 5 0,000 ft. 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 * 



It is during this Tertiary period that the mammals the 

 warm-blooded, hairy quadrupeds, which suckle their young 



* I am inclined to think that the line between Pliocene and Pleistocene 

 or Quaternary ought, in this country, to be drawn between the White and 

 Red Crag of Suffolk. Glacial conditions set in and were recurrent from the 

 commencement of the Red Crag deposit onwards. 



