PHYSIOGRAPHY. 



CHAPTER I. 



THE THAMES. 



No spot in the world is better known than London, and 

 no spot in London better known than London Bridge. Let 

 the reader suppose that he is standing upon this bridge, and, 

 heedless of the passing stream of traffic, looks down upon 

 the river as it runs below. It matters little on which side of 

 the bridge he may chance to stand ; whether he look up 

 the river or down the river, above bridge or below bridge. 

 In either case he will find himself in the presence of a 

 noble stream measuring, when broadest, nearly a sixth of 

 a mile from bank to bank. The quantity of water under 

 London Bridge varies considerably, however, at different 

 seasons, and even at different hours on the same day. When 

 the water is highest, the greatest depth is about thirty 

 feet and the width 800 feet ; when the water is lowest, the 

 greatest depth is something like twelve feet and the width 

 only 650 feet. This variation in the volume of water shows 

 that the river is not at rest, and that its surface is, in fact, 

 alternately rising and falling. Moreover, apart from the local 

 agitation due to traffic, apart too from the surface ripples 

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