Notices of Memoirs — W. Whitalcer's Address. 27 



separately, and it has been included with that of the overlying 

 division. In Norfolk neither of these come to the surface. 



The Woolwich and Beading Beds are \ery irregular and varying in 

 their composition, sometimes all clay, sometimes all sand, sometimes 

 alternations of clayey and sandy beds. As it would be almost im- 

 possible to pick out the pei'meable and impermeable parts, the whole 

 has been classed as mixed. In Norfolk and in the neighbouring 

 part of Suffolk, where these beds are everywhere thickly covered 

 with Drift, I have extended the colour of the impermeable beds up 

 to their presumed boundary, as a matter of safety. 



The Oldhaven and BlacMeath Beds, though of a highly permeable 

 character, are nearly everywhei'e underlain by the last division, and 

 therefore their permeability is of no effect, as regards the Chalk, so 

 that they have to go with the last, except in the very small areas 

 where they cut through to the Thanet Sand, and in the outliers that 

 rest direct on the Chalk. 



The London Clay has already been noticed ; but it should be re- 

 marked that its basal beds are often rather sandy, and let some water 

 through. The outcrop of these beds however is so small that it may 

 be disregarded. All the beds overlying this thick and widespread, 

 mass of clay are put out of court, as I have already said, being cut 

 off from the Chalk by it, and thus the Bagshot Beds and the Coral- 

 line Crag are wholly disposed of. 



The Bed Crag of Suffolk, however, in part rests on the Chalk, and 

 must then take its proper place among the permeable beds, though 

 most of it is taken out from the fact of overlying the London Clay. 

 With its representative in our county, the Norioich Crag, the case is 

 somewhat different, as it rests to a much greater extent on the Chalk. 

 As however, in the Geological Survey maps, some upper beds are 

 coloured with this series that have not always been classed with it, 

 we must take into consideration the occurrence of those clayey 

 patches, generally thought to represent the more continuous Chilles- 

 ford Clay of Suffolk, which locally cut off the gravel and sand above 

 from the Chalk, as far as infiltration is concerned, and as some of 

 these patches are too small to be shown on the map, though they 

 may have much effect underground, this is a case where local know- 

 ledge comes in, and I have to thank Mr. H. B. Woodward for giving 

 me the advantage of his knowledge in this matter. As a general 

 rule the Norwich Crag, has been classed as permeable, even where 

 the lower part is not seen, and where, though small lenticular masses 

 of clay or loam may occur, these would have little effect, merely 

 throwing off the water locally. 



The T)rift, as you must expect, has a very varying effect, from its 

 varying character. The Boulder Clay has already been noticed, and 

 there is no need to recur to it ; but the gravels and sands that often 

 underlie it, though in themselves permeable, are sometimes cut off 

 from the Chalk by clayey beds, whether thin local layers of Boulder 

 Clay or masses of brick-earth. With regard to this Glacial brick- 

 earth too there is much variation, for whilst most of the small isolated 

 masses in the south are practically impermeable, when we get to the 



