PEOPLE OF THE SUBMERGED FOREST 45 
It is believed ^ that the accumulation of a sheet of ice, 
several thousand feet in thickness, will depress that part 
of the earth's crust on which it rests. On the other hand, 
the part of the crust which lies immediately to the south 
of the ice-sheet will well upwards, it is believed, in the 
form of a wave, giving rise to such an elevation as is 
occurring in Scandinavia now. Still further south, beyond 
the wave of elevation, there is a secondary trough or 
depression. At the commencement of the Neolithic 
period, if we entertain the explanation just given, the ice- 
sheet was disappearing from North Britain, and England 
was elevated on the wave which follows the retreating 
edge of the ice. During the Neolithic period, as the ice- 
margin retreated further to the north, England was over- 
taken in the succeeding wave of depression — which 
apparently still continues. Such a hypothesis, purely 
speculative in nature, helps us to explain some of the 
phenomena with which we have to deal in future chapters. 
At least, it fixes in our minds the fact that the Neolithic 
age lies wholly within the milder period which followed 
the last long spell of glaciation. 
• See article by Dr John W. Evans, Nature^ 191 1, vol. Ixxxvii. p. 438. 
