Vol. 54.] EXPOSED IN THE CUTTING OP THE NEW BRUGES CANAL. 581 



have been ushered in by a slight overflowing of the peat by the sea, 

 and a deposit of clay, which hus allowed the peat to continue growing 

 contemporaneously with the deposit ol: clay, thus accounting for the 

 inosculation and the irregular, undefined surface of the peat. The 

 ground continuing to sink gradually, the Scrobiculatia-iAay alone 

 was laid down in beds from 1 to 6 metres thick, according to the 

 Belgian Survey. In these deposits, between tide-marks, Scrohicu- 

 laria plana ^ flourished, as it does now in the estuarine mud of the 

 Eiver Merse3\ 



As the submerged plain became levelled up with this deposit the 

 sea shallowed, and the thin bed, usually less than 1 metre thick, of 

 the Argile des polders inferieurc was deposited in places. 

 Upon this was laid down the Cardium-&aind, so rich in microzoa 

 and full of the remains of Cardium edtde. 



This bed, according to the Belgian Survey from 3 to 4 metres 

 thick, is a strikingly marine or estuarine deposit probably laid down 

 in water of greater depth than either the previous or succeeding 

 deposits. The water was again shallowed by the laying down oi 

 this sand, and by the final capping with the Argile des polders 

 superieure, upon the seaward margin of which the r^and-dunes 

 are now superimposed, and the artificial dykes built. 



As regards these estuarine clays and silts, the microscopic exami- 

 nation shows that much of the material has been directly or in- 

 directly derived from the underlying and surrounding Tertiary beds, 

 and their distinction lies in the rich abundance in which marine and 

 estuarine forarainifera and other microzoa of existing species occur. 



What struck me in these deposits, as compared with those that I 

 have mapped in North-west Lancashire and Cheshire, is their great 

 expansion or horizontal extent at levels varying so little, as is shown 

 in the Belgian Survey map. It would, in the British examples, be 

 impossible, even by a careful sj-stematic chain of borings, to trace 

 successive zones in the way that the Belgian geologists have 

 succeeded in doing. 



As regards age, all the estuarine beds described are later than 

 the peat representing the old land-surface, and this ])eat is newer- 

 looking than the peat of our Lancashire and Cheshire submarine- 

 forest bed, more nearly approaching the inland peat of Altcar and 

 Martin Mere. 



Discussion. 



Prof. Hull spoke. 



The AuTaoR, in answer to Prof. Hull, said that the peat in Galway 

 Bay between tides was shown to him by the late Prof. W. Kino- as 

 actually in process of growth. While the peat and forest-beds all 

 round our coasts indicated subsidence, the intercalation of thin seams 

 of peat in either the base or upper part of a purely estuarine deposit 

 such as >Scro'/2C'j/ar/a-clay, a phenomenon often seen, shows that the 

 peat w^as growing in slacks on the shore while the deposit was in 

 process of formation. 



^ [Sc.piperaia.] 



