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four feet above the slimy ooze below. And what purpose does 

 this vast sieve-like mass effect ? As the tide rushes in it bears 

 with it masses of decaying vegetable matter and detritus of 

 various kinds, which, when the tide runs out, is in large part left 

 behind. These, added to the decaying leaves which are constantly 

 dropping from the trees above, at length build up a slimy bottom, 

 which, eventually rising above the water, in time becomes solid 

 ground and fit for agricultural purposes. The continuation of 



Fig. 4. Rear of a mangrove swamp, showing its recession from the dry land. 



this process at last leads to the undoing of the mangrove itself, 

 for, being a lover of the water or of wet places, it finds the new 

 conditions uncongenial and begins to recede, thus vacating the 

 land which it has itself built up, and adding largely, year after 

 year, to the soil available for the purposes of man. In the fourth 

 illustration this stage of the development is depicted. Here may 

 be plainly seen the receding mangrove and the intervening strip 

 of barren land between it and the distant hillside, where the 



