TF. H. H'udkdon — Recent Wells in Dorset. 219 



The Higher Clay-series (B). — The fruits and plant remains are 

 approximately on the same horizon as those from Norden and 

 Bournemouth. 



The Second Sand-series (C). — The most interesting hed in this series 

 is the one indicated in the table as C, h, which contains such a large 

 quantity of water. This is composed of angular grains of a highly 

 crystalline quartz ; the larger fragments are dull or fatty, and range 

 up to -g-inch. There is also a considerable amount of dark-coloured 

 silicious fragments, such as go under the general term of 'lydite.' 



The Pipeclay Series (D). — As this group is only known from 

 boring, the arrangement of the details is somewhat arbitrary since the 

 several clays were much mixed. Thei'e can, however, be little doubt 

 that series D repi-esents the Pij^eclay Beds of the northern and 

 southern outcrops, though inferior to the clays of the southern outcrop 

 in quality. Much the same varieties of clay as we find in the Creech 

 district came up from the borehole, and there was no difficulty in 

 recognising the greyish-white pipeclays alternating with the inferior 

 or variegated varieties known in the workings as 'two-ball' clay. 



"When we come to speculate on what lies below the termination 

 of the borehole (215 feet from the surface), it is almost impossible to 

 predict what may be the thickness of the remainder of the Bagshot 

 Beds. Below the pipeclay series it is almost certain that another 

 sandy series would be encountered as constituting the base of the 

 formation, and there may be bands of iron grit such as occur on this 

 horizon at many places in the Isle of Purbeek. None of the Govern- 

 ment geologists, so far as I know, give us any assistance in estimating 

 the thickness of the Bagshot Beds at their full development in Dorset. 



" The Lower Tertiaries. — We may naturally conclude that both the 

 London Clay and the Reading Beds will have to be encountered ere 

 the Chalk can be reached. Yery little is known about these beds, 

 which are best studied, perhaps, on their outcrop in the Wool district. 

 In a borehole section it may not be very easy to distinguish between 

 Bagshots and London Clay, as the latter formation in this country 

 consists largely of sand. Probably the most distinguishing feature of 

 the London Clay is the amount of black flint pebbles which it contains, 

 and which are sometimes cemented by iron-oxide into a most intract- 

 able conglomerate. The Beading Beds are also mainly sandy, but side 

 by side with these sands are developments of mottled clays largely 

 used for brick-making. A total thickness of 100 feet for the London 

 Clay and Beading Beds is, perhaps, fairly approximate.^ It is quite 

 possible that some of these Lower Tertiaries may contain good water- 

 bearing beds." 



The main interest, from a geological point of view, consists in the 

 estimated thickness of the unproved Tertiary beds down to the Chalk. 

 As regards the Bagshot portion of this unknown quantity, I may refer 

 to two short memoirs by the Government Surveyor, Mr. Clement Reid, 

 F.E.S., "Geology of the Country round Bournemouth" (1898) and 

 "Geology of the Country round Dorchester" (1899), and although in 

 the question of the total thickness of the I3agshot system in the 



1 This estimate ^vas subsequently increased to 125 feet. 



