194 Marsh. 



about twenty grains of mineral matter. It has further been 

 calculated that this would amount to a daily discharge of 

 solid matter equal to one thousand five hundred and four- 

 teen tons, of which about one thousand five hundred tons 

 are in the form of chalk (carbonate of lime) and two hun- 

 dred and thirty-eight tons of gypsum (sulphate of lime). 



Whither does this solid matter go ? It is not all carried 

 to the sea, for the water around the mouth of the river has 



FIG. 40. KINGFISHER (Alcedo ispida). 



a much smaller proportion of both substances than is the 

 case higher up. Part of the solid matter is held in 

 suspension, and this is deposited as mud so soon as the 

 water becomes still enough. But it is the matter in solu- 

 tion for which we have to account. No doubt this is 

 mainly used by fishes and sea animals for the formation of 

 their bones or shells. A few miles below us is Whitstable, 

 celebrated for its oysters. It has been calculated that every 



