136 mr. a. j. jukes-browne on [May 1906, 



proportion of flints, and he states that it always contains a large 

 percentage of rounded quartz-grains, such as could not be derived 

 from the Chalk below. Again, among its contents in the country 

 north of Chichester he mentions the occurrence of flint-pebbles, 

 green-coated angular flints, sarsen-stones, and quartz-sand, these 

 ' and probably most of the clayey matrix, being of Eocene origin/ 

 Mr. Reid also makes the explicit statement that 



' in this part of the Downs (near Chichester) it is confined to areas over which 

 Eocene deposits may have spread within comparatively recent times; it is 

 sometimes very difficult to decide whether a particular patch should be called 

 slightly-disturbed Eocene, or mapped as Clay-with-Flints.' (Loc. supra cit.) 



With the truth of this statement, as applied to other districts, I 

 shall deal more fully in the sequel. 



The same observer, describing the deposit as developed near 

 Salisbury, 1 writes that ' parts of it are mainly composed of Eocene 

 material,' and ' other parts are derived in large measure from the 

 Chalk below.' He adds : 



'Everywhere, however, there is a considerable admixture of material that 

 cannot have been derived from the strata immediately below. We find in it, 

 for instance, Chalk-flints belonging to zones which only outcrop some distance 

 away on higher ground. It also contains pebbles derived from Tertiary 

 deposits, which cannot have rested directly on the Chalk in that neighbourhood. 

 On washing the matrix we obtain a sandy residue consisting of rounded grains 

 of quartz, such as could not have been derived from the Upper Chalk.' 



Again, in Dorset the proportion of material that must have been 

 derived from the Eocene is still larger, and Mr. Reid observes : 



' At least half the deposit consists of rolled stones and rounded quartz- 

 grains. . . . Even of the angular material, a close examination shows that a 

 considerable proportion must be derived from the gravelly base of the Eocene 

 deposits, in which angular flints usually abound.' 2 



He asserts, indeed, that 



' over the area now under consideration solution of the Chalk and accumulation 

 of the insoluble matter will not produce anything approaching in composition 

 to the Clay-with-Flints.' {Loc. cit.) 



My own observations in Wiltshire and Dorset confirm those of 

 Mr. Keid, especially on the point that, where the deposit is most 

 argillaceous and most essentially a Clay with flints, it is still 

 obviously and largely composed of Eocene material. 



With regard to the finer portions of the Clay-with-Flints, it will 

 be noticed that Mr. lleid has found that, both in Sussex and in Dorset, 

 it invariably contains a large percentage of rounded quartz-grains. 

 Mr. Osborne White tells me that he has washed many samples of 

 the material from the neighbourhood of Heading and Wargrave, 

 and has always found a residue consisting largely of quartz-sand. He 

 has kindly sent me a sample of the Clay-with-Flints, overlying the 

 Chalk in a quarry at Middle Culham, near Remenham (Berkshire) ; 



1 Expl. of Sheet 298, Mem. Geol. Surv. 1903, p. 64. 



2 ' Geology of the Country around Dorchester ' Mem. Geol. Surv. 1899, p. 37. 



