1 68 WORGRET HILL AND WAREHAM WATER SUPPLY. 



Bagshots. The chief element of uncertainty lies in the fact 

 that the pipeclay series was not gone through, but we may 

 assume almost with certainty that a third Bagshot Sand-series, 

 with a development of 60 or 70 feet, would still t^e to be 

 encountered ere the Lower Tertiaries were reached. 



When the next engineer tries to bore through the beds 

 comprising the Wareham syncline he must not forget that, after 

 penetrating the Bagshots, he still has to deal with the Lower 

 Tertiaries, i.e., the London Clay and Reading Beds. Thus a 

 fairly correct estimate of their combined thickness becomes a 

 matter of importance to the general problem. On reference to 

 the Tabular Column (Fig. 4) it will be seen that a development 

 of 100 feet was hypothetically assigned to these beds. The 

 London Clay of Dorset, like that of the Thames basin, where it 

 is so much more important a formation, is believed to be of 

 marine origin, whilst the Reading Beds are regarded as 

 fluviatile. From a palaeontological point of view both are 

 extremely unsatisfactory, and if the London Clay of Dorset 

 really is a marine formation, the total absence of fossils has 

 received no explanation. To judge the thickness of these beds 

 at Worgret with accuracy is no easy task. In Studland Bay the 

 Reading Beds are estimated by Mr. Strahan (Geology of 

 Purbeck, etc., pp. 170 and 191), at from 50 to 60 feet, and the 

 London Clay, he considers from its outcrop, to have a thickness 

 of about 80 to 100 feet. The minimum thickness of the Lower 

 Tertiaries at Studland, therefore, would be 130 feet, and the 

 maximum 160 feet, mean 145 feet. Studland Bay is, of course, 

 a considerable distance from Worgret, and there might be some 

 diminution of volume. In the Spyway boring near Moreton, as 

 we have seen, a borehole started in the London Clay passed 

 through 90 feet of beds before reaching the Chalk. This gives 

 us a minimum of 90 feet for the Lower Tertiaries without 

 including any part of the London Clay which may be above the 

 mouth of the borehole at Spyway. It would probably be safe to 

 add some 20 or 30 feet to my original estimate of the Lower 

 Tertiaries as given in the tabular column of the report. Hence, 



