GREENSAND AND PALEOZOIC ROCKS UNDER LONDON. 911 



sunk, and then a bore-hole was carried down the rest of the way. 



The section obtained was as under*: — 



ft. 



Soil and Chalk rubble 13 



Chalk without flints (very hard) 112 



Chalk marl (very argillaceous) 88 



Upper Green sand 10 



Gault 226 



Lower Greensand (sand and sandstone) 26 4- 



475 



On reaching the Lower Greensand the water rose in a trial-pipe 

 fixed into the bore-hole to a height of 12 ft. (or rather more) above the 

 surface of the ground. But unfortunately, from the loose character 

 of the beds and the small size of the bore-hole, it got largely filled 

 with the sand, and the delivery of water has consequently always 

 remained very slow and small. Added to this, the water is slightly 

 ferruginous and, with the slow discharge, has shown but little im- 

 provement ; still, after settlement, it is quite potable. 



The experiment is nevertheless one of great interest, and the 

 result would, there can be no doubt, have been far more successful 

 could the tubes be properly cleared of sand. The thickness of the 

 Gault is unusual. 



Combining the several data now in our possession, the accom- 

 panying section (fig. 5) shows the probable position and range of the 

 Lower Greensand and the position of the Palaeozoic rocks under the 

 London Basin. 



In short, while there is every reason to hope that, on the south 

 of London, we may yet find in the Lower Greensand, beneath the 

 Tertiary strata and Chalk, a source of large and valuable water- 

 supply for metropolitan purposes, there is strong reason to believe in 

 the probability of the discovery to the north of London of Carboni- 

 ferous strata, including possibly productive Coal-measures, under the 

 same Cretaceous formations f . The position assigned to the latter 

 in the diagram is merely hypothetical. Even if the beds at Kentish 

 Town are lower in the series than those of Messrs. Meux & Co.'s 

 boring, the Palseozoic strata are so disturbed and folded that neither 

 the dip nor the relative position of the Devonian beds afford any 

 certain guide to the position of the Carboniferous trough. 



It is to be hoped that the accuracy of the geological hypothesis 

 may ere long be tested by a series of carefully considered and sys- 

 tematic trial-borings in the neighbourhood of London, and the solu- 

 tion of these two important problems effected. 



* The boring was made by Messrs. F. R. Baker and Sons, to whom and 

 Mr. Mildmay I am indebted for these particulars. 



t The westward prolongation of this underground belt of Palaeozoic strata is 

 not only indicated by the various pebbles of crystalline and metamorphic 

 rocks met with in the Lower Greensand, and by the shore-conditions of this 

 formation at Faringdon, but also by the apparent presence of the Trias under 

 the Great Oolite at Oxford (as suggested by the author in a paper " On a 

 Mineral Spring at Oxford," Proc. Ashmolean Soc. for 1876) ; while the exis- 

 tence of the Coal-measures themselves has recently been proved under the 

 Jurassic series and the Trias near Burford, on the confines of Oxfordshire and 

 Gloucestershire. 



