122 A SUPPOSED NEOLITHIC SETTLEMENT. 



simple. The lowest formation visible anywhere is the London 

 Clay, which appears here and there in the river-valleys. Above 

 the London Clay, and chiefly in the river-valleys, may be seen 

 the sand and gravel of the Glacial Period. Above this sand and 

 gravel, and forming the surface of the plateau between the 

 valleys, is the Chalky Boulder Clay. Then, here and there on 

 the plateau, are patches of gravel and loam resting upon the 

 Chalky Boidder Clay, and usually occupying slight depressions 

 on its surface. These last-named deposits (which are post- 

 Glacial in the sense of being of later date than the Boulder Clay) 

 are extremely irregular in their occurrence and in the space they 

 occupy. They have sometimes been foimd to contain mammalian 

 remains of interest, as in the brickyard at Great Yeldham, of 

 which some account is given in the Essex Naturalist (vol. ix., 

 pp. 115--118). All the beds liitherto mentioned are widely dis- 

 tributed, for though the lower are seldom visible, except in the 

 river-valleys,, they are found over considerable areas of country 

 beneath the higher beds. In addition, there are deposits which 

 are wholly confined to the river-valleys, liaving been formed by 

 the streams at various periods during the erosion of their 

 valle\ s. These are all of later date than the others mentioned, 

 the most recent being the alluvium occup\'ing the flat ground 

 close to the streams. No older river deposits, tomied when the 

 river had not cut down its channel to the present level, are shown 

 on the Geological Survey Map as manifestly existing within three 

 or four miles of Braintree. For the older the tenace, the longer 

 the time sinre its formation during which it has been subject to 

 destructive influences, whether those resulting from the mean- 

 dering of the stream or from the ordinary action of the weather. 

 Then, while fragments of terraces cut in comparatively hard 

 rock often remain clear and distinct, those cut in sijft material, 

 like London Clay or Glacial Gravel, soon cease to be traceable ; 

 and the difficulty of identifying them is at its highest in narrow 

 valleys like those around Braintree, where any river terrace can 

 never have been more than a few yards in breadth, and where, 

 consequently, its distinctively terrace-like aspect can never have 

 been very conspicuous. However, the obscurity that prevents 

 any beds of this kind from being mapped at Braintree by no 

 means implies that they do not exist there. In the Geological 

 Survey Memoiv on Sheet 47-f (which includes Braintree, Cog- 



t The Gcolof;y of the AMI', part of Essex and the S.E. part of Herts., with parts of Cam 

 bridgeshire and Suffolk. Hy W. Whitaker, W. H, Punning. W. H. Ualton, and F. J. Bonnett 

 London, 1878. 



