46 Origin of the British Flora. 
give place to a higher race that tilled the ground and had 
domesticated animals. These, however, are merely sug- 
gestions; for a systematic study of the deposits of this 
stage also, at some point where they give a continuous 
record, will probably solve the riddle. 
The Neolithic and later periods do not call for any 
lengthy description. At first the land stood at an elevation 
some 60 or 70 feet above its present level, so that many of 
the river-valleys were cut to that depth below the sea, and 
much of the English Coast was fringed with a broad strip 
of alluvium, which probably almost connected our island 
with Belgium and France. The climate during this epoch 
was Temperate, for in the lowest ‘submerged forests’ the 
Oak is the most abundant tree. Then gradual and inter- 
mittent submergence flooded the lower parts of the valleys, 
and caused them to be silted up by the deposits of rivers 
that no longer had sufficient fall to scour their beds. In 
some of the peaty deposits or old vegetable soils that mark 
stages of rest in their process of submergence, we find 
polished stone weapons, and relics of cultivated plants and 
of domesticated animals. The flora of these deposits, 
however, is still very imperfectly known; but all the plants 
are species still found in Britain, though the occurrence in 
South Wales in a ‘submerged forest’ of Mayas marina, a 
plant now confined to Norfolk, shows that the local 
distribution may have been slightly different. 
Since the close of the Neolithic Period, changes in 
physical geography have been slight, and have consisted 
mainly in the continuous silting up of the flooded valleys, 
and in the cutting back of the coast-line by the waves. 
This latter process, it should be remembered, has been 
sufficiently marked to increase the width of the Strait of 
Dover, which in places is also being deepened by the 
scour of the tides. When our present flora entered the 
