232 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 24, 



to 6 metres deep. The blocks left for measuring the work done 

 show such sections as the following : — 



{Yellow sands, gravel and broken shells. 

 Grey sands, numerous broken shells. 

 Brown sands. 



(Pale-green sands, shells few, not much broken. 

 Dark-green sands, Pectunculus-h&nd. 

 Very dark compact beds. 



The relative thicknesses vary much from place to place; the whole 

 not being more than 12 feet thick, of which the upper brown and 

 yellow sands form about 6 feet. In the Dock-sections these upper 

 beds may have been somewhat thicker, but at no place do they pro- 

 bably exceed 8 feet. 



The upper series (a) constituting the " JSysteme ScalcUsien" of 

 M. Dumont, viewed as a marine accumulation, presents a very com- 

 mon condition of sea-bed, consisting of dead-shell gravel, mostly 

 forming banks, and heaped up under inconsiderable depths of water. 

 This is a good division of the series, inasmuch as it marks a change 

 in the depth and moving power of the water at this particular spot, 

 the result, doubtless, of a physical change of wider extent; the 

 effect of which was the disturbance of previously formed sea-beds 

 and their rearrangement. At the same time there was an outward 

 distribution of the materials of a higher or sublittoral zone, as seen 

 in the gravel. 



The " Systeme Scaldesien," as exhibited at Antwerp in the form 

 of " couches remanies," very closely resembles both in the condition 

 of its materials and fossils, the Red Crag beds of Suffolk ; nor is 

 there any reason why the physical change which caused the 

 Eed Crag to succeed the Bryozoan should not be referred to the 

 same geological change which made the Scaldesien follow on the 

 Diestien. 



3. Systeme Diestien. — In the section given above, which is just 

 such as is to be seen everywhere from the Porte de Tournhout to 

 that of Malines, the Scaldesien beds, or yellow and grey coarse series, 

 contain either fine pale-green, somewhat loose sands, or else dark- 

 green, almost black, and compact sands ; these are the Diestien beds 

 of Dumont. With reference to condition of sea-bed, it is that form 

 well known as deep-water sandy and muddy ooze, and was the de- 

 posit of tranquil depths. 



Although the whole thickness of this lower series has not been 

 cut through within the area of the fortifications, even in the section 

 above referred to, which presents the deepest cuttings, yet it has 

 been proved, as we were informed by the Engineer ofiicers on the 

 spot, that the Diestien beds extended only a few feet below the 

 excavations for the main ditch, and that within the area as well as 

 without, the dark-green Diestien beds overlie compact Eupellien 

 clay. 



A maximum thickness of about 4 metres may be assigned to the 

 Diestien beds ; generally they are less, and small as are the vertical 



