XL] LONDON CLAY BED. 275 



water holding silex (flint) in solution a very rare 

 occurrence : but something similar is still going on in 

 the famous Geysers or boiling springs of Iceland. 

 However, I have no proof that this was the cause. I 

 suppose we shall find out some day how it happened ; 

 for we must never despair of finding out anything 

 which depends on facts. 



Part of the town of Odiham, and of North Warn- 

 borough, stands, I believe, upon these lower beds, 

 which are called by geologists the Woolwich and Read- 

 ing beds, and the Plastic clays, from the good brick 

 earth which is so often found among them. But as 

 soon as you get to Hook Common, and to Dogmersfield 

 Park, you enter on a fresh deposit ; the great bed of 

 the London clay. 



I give you a rough section, from a deep well at 

 Dogmersfield House ; from which you may see how 

 steeply the chalk dips down here under the clay, so 

 that Odiham stands, as it were, on the chalk beach of 

 the clay sea. 



In boring that well there were pierced : 



Forty feet of the upper sands (the Bagshot sands), 

 of which I shall speak presently. 



Three hundred and thirty feet of London clay. 



Then about forty feet of mottled clays and sands. 



Whether the chalk was then reached, I do not 

 know. It must have been close below. But these 

 mottled clays and sands abound in water (being indeed 

 the layer which supplies the great breweries in London, 

 and those soda-water bottles on dumb-waiters which 

 squirt in Trafalgar Square) ; and (I suppose) the water 

 being reached, the boring ceased. 



Now, this great bed of London clay, even- more 



T 2 



