§ 25. THE HAMPSHIRE BASIN. 237 



The wells in London vary in depth from 100 to 600 feet ; 

 but the total thickness of the clay in some places is estimated 

 at nearly a thousand feet. The most remarkable instance 

 of success in obtaining a perennial fountain from a deep 

 source, by the process of boring above described, is the 

 Artesian well at Grenelle, near Paris, which was carried 

 through the entire series of the tertiary and cretaceous 

 strata, down to the green sand ; a depth of 1,800 feet ! 

 The water rises in a powerful column to the height of 

 thirty feet above the highest part of Paris, and has a 

 temperature of 91° Fahrenheit, being sufficiently hot for 

 warming greenhouses, &c. 



25. The Hampshire basin. — The London basin does not 

 present an alternation of marine and fresh- water deposits, 

 like that of Paris ; but in Hampshire and the Isle of Wight, 

 there is an extensive suite of tertiary, composed of fresh- 

 water clays, sands, and limestones, associated with marine 

 strata. This series extends over a considerable dis- 

 trict. On the east, a small outlier of the lower beds of 

 plastic clay appears at Castle Hill, near Newhaven, in 

 Sussex ;* and to the west of Brighton, the London clay 

 rises to the surface, and forms the subsoil between the 

 Downs and the sea-shore. The inland boundary of these 

 tertiary strata stretches by Chichester, Emsworth, and 

 Southampton, to Dorchester ; and the London clay is 



or lying inclined in a direction from the central plateau of London ; 

 but the chalk forms a deep gulf or excavation, in which the Lon- 

 don clay is situated, and thus the drainage from the surrounding 

 chalk hills flows into the centre of the basin, and furnishes an almost 

 inexhaustible reservoir. I need not add, that attempts to obtain 

 water by Artesian borings in any chalk district, where the strata are 

 horizontal or inclined, will fail, unless the beds immediately upon 

 the chalk-marl could be reached. The borings for water near South, 

 ampton exemplify these remarks. See my Geology of the Isle of 

 Wight, p. 81. 

 * Geology of the South-East of England, p. 53. 



