220 EXCAVATIONS AT DEWLISH. 



An interesting section was laid bare during the excavation 

 of the trench on its northern wall, which threw an instruc- 

 tive light on the problem of the trench's origin. The 

 accompanying diagrammatic section * shows the depth of the 

 trench and the configuration of its northern wall. From 

 the surface to the base the trench is roughly seventeen feet 

 deep ; the wall, however, is not vertical, but is diversified 

 into rounded steps separated by perpendicular walls. The 

 first six feet from the top is a vertical wall of chalk (a) 

 smoothed and with channels running down from top to 

 bottom ; beneath this wall and jutting out into the trench 

 is a cupshaped hollow or basin (b) quite smooth inside, 

 but only a few inches deep. The lip of the basin is cut 

 through by channels which are continuous with other grooves 

 running down a second vertical smooth face (c) some two 

 feet deep. This face also terminated in a shallow basin (d) 

 with a channelled lip, beneath which the smooth vertical 

 face was traceable to the base of the trench (e). The structure 

 represents in fact a fossil waterfall with characteristic pot- 

 holes and smoothed faces and channels. 



Pinnacles of chalk rise from the base of the trench at 

 its higher end, while much lower down the hillside 

 the bottom of the trench is undulating, hummocky, and 

 quite smooth, and when fine sand was swept with a birch 

 broom it poured down over the hummocks like water in a 

 cascade. And it is indeed probable that at this part of its 

 course the water of the torrent did form cascades as it rushed 

 towards the valley bottom. 



There is, however, a sequence of events represented at 

 Dewlish, for the trench was filled with two sorts of deposits, 

 each one being confined respectively to its northern or southern 

 sides. 



The earlier deposit is an exceedingly fine dust-like sand of 

 a pinkish grey colour. This rested in even-bedded 

 and false-bedded layers against the northern wall of the 



* See folding plan. 



