^ mithe London and Hampshire Basins. 449 



ham Bay to Chichester Harbour, is occupied by the boulder- 

 drift. The line of demarcation of these two kinds of drift runs 

 nearly parallel with,, and close upon the protruded chalk-anticlinal 

 above described*. I have not been able to find evidence of the 

 existence of the boulder-drift west of Chichester Harbour, in 

 Thorney or Hayling, and it dies out as we come north from Sel- 

 sey, though there is ample proof of its ancient extension over a 

 much larger surface ; blocks of granite and of other crystalline 

 rocks are found at Siddlesham, Hounston Common, and in Bird- 

 ham. The occurrence of these granitic boulders on the Sussex 

 coast w^as first noticed by Mr. Dixon in his summary of the Geo- 

 logy of the Bracklesham district f; he does not seem, however, 

 to have been aware of their importance, or to have understood 

 the true geological relations of the deposit in which they were 

 found. Mr. Godwin Austen has also recognized the existence of 

 this deposit, and has described and speculated on it in a paper 

 read before the Geological Society, of which an abstract is given 

 in the ' Quarterly Journal,' vol. xii. p. 4. It is composed of loam 

 or brick-earth, extensive beds of rounded gravel and angular flint, 

 the former much predominating, with here and there large erratic 

 blocks, the whole exhibiting the heterogeneous and tumultuary 

 character of the boulder-drifts of the eastern counties. Of the 

 position and the true geological relations of this important de- 

 posit more will be said by-and-bye ; for the present it will be 

 well to return to a further consideration of the angular flint, or — 



Diluvial Drift. — Much valuable detail of the nature and dis- 

 tribution of this drift has been given by Sir R. I. Murchison in 

 his paper ^' On the Flint Drift of the South Downs " (Quarterly 

 Journal of the Geological Society, Feb. 1, 1852). The soil of 

 the greater part of the flat country under review is entirely com- 

 posed of it, and it lies especially deep between the base of the 

 Downs and the chalk-anticlinal above described. An attentive 

 study of the country, with a due consideration of the nature of 

 the stratified beds below, and of the convulsive changes they 

 have undergone, must bring the conviction that the loams, brick- 

 earths, beds of impacted angular gravel, and all the other super- 

 ficial phsenomena of this deposit, are the result of diluvial cur- 

 rents operating through geological periods more or less prolonged, 

 and recurring at longer or shorter intervals. 



Good illustrative sections of these gravels are to be seen on 

 each side of the road from Slindon Common, where Sir R. Mur- 

 chison says they appear in great force, to Chichester. At Ball 

 Hut they are loosely mixed up with the sands of the lowest 



* This line of demarcation is not sharp and well defined, but there is a 

 manifest and marked difference north and south of it. 



t Dixon's * Geology of Sussex/ p. 14. ;.^i:. ,i '. 



