1912.] 



DISCOVERY OF A CIST. 



413 



L'Ancresse. These lines are lines of interruption when the 

 clay deposit was arrested and vegetation grew undisturbed. 



The clay deposit was not confined to the mound proper 

 but thinned out to smaller layers to the N. and S., and at 

 considerable distances from the dolmen the neighbourhood 

 showed the same layering and stratification. 



The black mould may be associated with the submerged 

 forest period in its last phase. The conditions under which 

 it was formed were altogether different from the present ones 

 for tha sea had not yet broken in the Braye. 



Whether that had occurred before the dolmen builders 

 erected their structure or not cannot be said, but it is probable 

 that the coast line was still outside the last barrier in Grande 

 Havre before the inundation of the Braye at the time they 

 chose the spot, for it seems unlikely that they would have 

 chosen a spot the foot of which was being washed by the sea. 



The dolmen builders therefore saw no sea in the imme- 

 diate neighbourhood of their mound, but not long after this 

 time the barriers in Grande Havre were broken through by 

 the joint action of the sea and the advance of sea level, and 

 the sea entered into the low lands of the Braye du Valle. 



At first this would not influence the spot, but in course of 

 time the insular position of the low hill was developed, and 

 the sea at high tide lapped the base of the hill very nearly in 

 the positions of the present roads. 



When the present sea level was reached, Grande Havre 

 was practically open sea, and the Braye du Valle was swept 

 by storm waves. 



These storm waves, when they occurred coincident with 

 spring tides, swept over the mound on which the dolmen 

 stands and washed away everything except the stones. But 

 the stones of the alignment of the circles, the smaller cap 

 stone of the minor graves and the closing slab of the dolmen 

 were displaced and the bones were washed out. The smaller 

 graves and the bottom of the larger one received the mould- 

 earth and blackened stones lying about from the building 

 operations. 



Clay was torn up from the lower levels of the old beach 

 and washed up, forming slowly and gradually a kind of upper 

 head of very much larger area than found during our excava- 

 tion. Much of this was rain-washed into the central dolmen. 



Some cessation of the action occurred, during which the 

 mound of clay was reduced in size by rain-wash, the mega- 

 lithic structure acting as a stop and an oval-topped mound 

 resulted. This in its turn was covered by blown sand, and in 

 our day this was overgrown by wild plants. 



