THEORY OP THE EARTH. 51 



Lakes, low meadows, marshes, and sea-ports, into 

 which rivulets discharge their waters, more espe- 

 cially when these descend from near and steep 

 hills, are continually receiving depositions of mud, 

 which would at length fill them up entirely, if they 

 were not carefully cleaned out. The sea is con- 

 stantly accumulating quantities of sand and slime 

 into its bays and harbours, or wherever its waters 

 happen to become more quiet than ordinary. The 

 currents also occasioned by the tides, are con- 

 tinually washing large quantities of sand from the 

 bottom of the sea, which they collect together and 

 heap up on various parts of the coast, forming 

 banks and flat shallows. 



14. Of Stalactites. 



Certain waters, after dissolving calcarious sub- 

 stances by means of the superabundant carbonic 

 acid with which they are impregnated, allow these 

 substances to crystallize, in consequence of the 

 escape of the acid, and in this way form stalactites 

 and other concretions. There are some strata, 

 confusedly crystallized in fresh water, which are 

 sufficiently extensive to be compared with other 

 strata that have been left by the ancient sea. 



15. Of Lithophites. 



In the torrid zone, where lithophites of many 

 kinds abound, and are propagated with great ra- 



