AN EARLY NEOLITHIC KITCHEN-MIDDEN. 69 



overhanging rocks of a waterfall ; for in such places the disturbance 

 of the water causes the most rapid freeing of the excess of carbonic 

 acid and consequent deposition of the lime. The Blashenwell tufa 

 fills a shallow depression sloping gently towards the north-east. 

 The material being used for marling the land, three pits have been 

 opened in it, the largest and most interesting lying close to the road 

 about 250 yards north of the farm. A few yards to the north-west 

 the margin of the deposit was proved by boring ; and the ancient 

 settlement about to be described seems to have lain on the dry 

 bank immediately above the stream at that spot. In this pit the 

 dip of the tufa is made conspicuous by a seam containing enough 

 scattered charcoal to change the normal cream-colour to grey, and 

 by its parallelism to the present soil to show that the surface 

 contours have not since been altered by erosion. The general 

 section in this pit is roughly as follows : 



Feet. 

 Black soil : at its base Roman coins, Romano-] 



British pottery, shells of oyster, whelk, cockle, Y 1 



Helix aspersa, H. ericetorum, H. virgata, &c. J 

 Hard tufa with leaves of hazel, elm, and oak. land-" 



shells, flint-flakes, and charcoal. 

 Granular tufa, fairly soft, flint-flakes, bones of pig 



and deer, limpets and other marine shells, land 



snails, including Glausilia laminata, Bulimus 



montanus, &c., much charcoal. 

 Loamy and marly tufa, with small land-shells, 



occasional Limncea truncatula, rare flint-flakes, 



and charcoal. 



Loam with stony base. 



The contrast between the black soil full of fragments of Roman 



or Romano-British pottery, and cream-coloured tufa below is very 



marked. The Roman layer was deposited when the tufa had 



ceased to form, and it is noticeable that not only the pottery but 



the three most abundant snails found in it are entirely missing in 



the tufa below. 



