1826.] Geological Society/. 393 



formation. They occupy an interval in the coast of about 16 

 miles in extent, between the London clay of HighclifF on the 

 east of Muddiford and the chalk of the Isle of Purbeck. A 

 coloured section of the strata exhibited in these cliff's accompa- 

 nies the paper. The author first described in detail the cliffs of 

 Christchurch, or Hengistbury Head, which consist of sand and 

 loam, often much charged with bituminous matter, and contain- 

 ing large concretions of ferruginous sandstone and clay iron- 

 stone, disposed in fine parallel layers, in which, as well as in the 

 sand and loam, occur black-flint pebbles, lignite, and flattened 

 impressions of fossil trees. Below these strata are dark bitumi- 

 nous clays, alternating with red and brown sands, with occasional 

 layers of black-flint pebbles. After the outcrop of the above 

 strata, the chfi^s are low, and about three miles from Muddiford, 

 are composed solely of diluvium. When they rise again in 

 height, their direction corresponds with the hne of bearing of 

 the strata, so that the same beds are continuously exposed for 

 eight miles, as far as the mouth of Poole Harbour. 



These beds consist of fine white sand, pinkish sand, and thinly 

 laminated argillaceous marles, containing occasionally much 

 vegetable matter; and the whole series exceeding 150 feet in 

 thickness. The section is interrupted for a space of 2^ miles 

 by the mouth of Poole Harbour, and the bars of sand on each side 

 of it. But in the cliffs near Studland, the strata are again seen, 

 consisting principally of yellow and purplish sand, white sand 

 alternating with thinly laminated white clay, and sand with fer- 

 ruginous concretions passing into sandstone and pipe clay. 



The junction of the chalk with the superior strata is very 

 indistinctly exposed, but a thin bed of striated soft chalk-marl 

 rests immediately upon the chalk, as is the case in Alum Bay. 

 The author concludes with observations on the diluvium of this 

 district, composed chiefly of chalk flints, and he infers from its 

 local characters, both here, and in the rest of Hampshire, as 

 well as in the district between the North and South Downs, that 

 it owes its origin, in this part of England, to causes much more 

 local in their operation than those generally assigned. He 

 examines how far the phsenomena attending its distribution are 

 consistent with the supposition, that the diluvium was formed 

 in consequence of the protrusion of the inferior through the 

 superior strata, along the anticlinal axis which now separates the 

 tertiary basins of London and Hampshire. Admitting that this 

 elevation took place when all the strata were beneath the level 

 of the sea, Mr. Lyell endeavours to show, that the returning 

 waters, when the land was raised to its present position above 

 the sea, would have strewed the debris of the older over the 

 newer formations, as we now find it ; while those of the more 

 recent would not cover, except in inconsiderable quantities, the 

 more ancient strata ; and that the marked dissimilarity between 



