THE 



LONDON AND EDINBURGH 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[THIRD SERIES.] 

 MAY 1840. 



LVII. On the Boulder Formation, or drift and associated 

 Freshwater Deposits composing the Mud-cliffs of Eastern 

 Norfolk. By Charles Lyell, £5?., V.P.G.S , F.R.S.^SfcJ^ 



'T^HE cliffs extending from Happisburgh or Hasborough 

 ^ light-house to near Weybourne, north-west of Cromer, in 

 Norfolk, comprising a distance of about 20 miles, are desig- 

 nated in some maps as " the mud-cliffs." They are for the 

 most part composed of deposits of two kinds, first, stratified 

 and unstratified driit, called by some " diluvium ;" secondly, 

 freshwater strata. Both of these rest on chalk, which is usually 

 concealed below the level of the sea. Occasionally between the 

 chalk and drift or the chalk and freshwater beds, a thin layer 

 is found of marine crag, agreeing in its fossils with that of 

 Norwich, but occurring only in patches of small extent, ex- 

 cept near Weybourne, where it is more continuous. 



The drift, which sometimes attains a thickness of more than 

 300 feet, consists principally of clay, loam, and sand, in some 

 places stratified, in others wholly devoid of stratification. 

 Pebbles, and in some places large boulders of granite, por- 

 phyry, greenstone, lias, chalk, and other transported rocks are 

 interspersed, especially in the unstratified portion. Pure and 

 unmixed white chalk rubble, and even huge fragments of so- 

 lid chalk, are also associated in some localities. No fossils have 

 been detected in this drift which can positively be referred to 

 the aera of its accumulation ; but besides the organic remains 

 derived from secondary strata, it contains almost everywhere 

 broken fragments of shells which agree in species with those 

 of the Norwich crag, from which there is good reason to be- 

 lieve them to have been washed out. 



* Comnninicated by the Author. 

 Phil. Mag. S. 3. Vol. 16. No. lOt. May 1840. 2 A 



