GEOLOGY 



here the earliest traces of man ; but since the lake-bed was visited by Mr. 

 Clement Reid a few species of mammals have been added to his list and 

 a few flint implements have been found associated with them in this silt. 

 It therefore seems probable that primaeval man lived on the shores of this 

 lake and there fashioned his rude implements of flint, but we cannot be 

 certain that this was the period of his arrival in Britain. We do not find 

 the remains of man in these deposits, but only the results of his handiwork 

 in rudely-chipped flints. If, therefore, man existed in Britain before he 

 became a tool-maker we should have no trace of such existence. 



In a somewhat similar situation near Caddington Mr. Worthington 

 Smith has found a workshop of Palaeolithic flint implements ; he has 

 found the cores from which chips have been struck, and he has found the 

 chips struck ofF them and pieced them together again. Here there are 

 also other indications of human habitation, and, as at Hitchin, by the 

 side of a lake. 



With the advent of man the geological record ceases and the 

 archaeological begins, but there are other superficial deposits which have 

 not yet been noticed. Such are the detritus of existing rivers, whether 

 gravel or alluvium, sometimes much higher than their present level, 

 showing how deep they have cut down their beds ; and accumulations 

 of peat resulting from vegetable growth on boggy land. 



There are also deposits to which no definite age can be assigned, 

 in addition to those of which the age is a subject of controversy. The 

 formation of ' pipes ' in the Chalk has been going on ever since the Chalk 

 was raised above sea-level and water percolated into it ; and ever since the 

 Tertiary beds were removed from the surface of the Chalk, that surface 

 where exposed has been ' weathered ' into clay-with-flints, this bed, 

 which covers much of the Chalk in western Hertfordshire, being the 

 result of surface-disintegration of chalk. Much of our brick-earth has 

 also been forming for an indefinite period. 



A brief summary may now be given of the foregoing attempt to 

 trace the history of Hertfordshire before the advent of man, from which 

 period the story will be continued by Sir John Evans. 



The scene opens with a deep sea in which a calcareous deposit was 

 forming a sea teeming with the abundant life which characterized the 

 Upper Silurian period. The nearest land-surface was a plateau of 

 Cambrian rocks in the centre of England, the sea extending on the south 

 to western France, where it washed a shore of Cambrian and Lower 

 Silurian rocks. The sea-bed rose, and the calcareous mud, consolidated 

 into shale and limestone, became crumpled up into folds running east and 

 west, and on the southern flank of one of these folds there was sea in 

 Upper Devonian times, also replete with life. This sea-bed rising, its 

 sediment, consolidated into shale, remained for long ages a ridge of 

 land stretching across Middlesex and the south of Hertfordshire, the 

 highest part of this land being the Silurian hills on the north. Further 

 crumpling or folding in nearly the same direction as before affected 

 this Devono-Silurian tract so that the portion of it which has been dis- 



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