484 



CONCLUDING REMARKS ON DELTAS. 



[Ch. XIX. 



tlian sufficient to counterbalance all the efforts of the two 

 mighty rivers to extend the limits of their delta. We have 

 seen that the Artesian borings at Calcutta attest, what the 

 vast depth of the ' swatch ' may also perhaps indicate, that 

 the antagonist force of subsidence has predominated for 

 ao-es over the influx of fluvial 



mud 



from 



tion of the bay. 



CONCLUDING REMARKS ON DELTAS. 



>/ 



— If we possessed an accurate series 



greater. 



of maps of the Adriatic for many thousand years, our re- 

 trospect would, without doubt, carry us gradually back to 

 the time when the number of rivers descending from the 

 mountains into that gulf by independent deltas was far 



The deltas of the Po and the Adige, for instance, 

 would separate themselves within the Post-tertiary era, 

 as, in all probability, would those of the Isonzo and the 

 Torre. If, on the other hand, we speculate on future 

 changes, we may anticipate the period when the number 

 of deltas will greatly diminish; for the Po cannot con- 

 tinue to encroach at the rate of a mile in a hundred years, 

 and other rivers to gain as much in six or seven centuries 

 upon the shallow gulf, without new junctions occurring from 

 time to time ; so that Eridanus, ' the king of rivers,' will con- 

 tinually boast a greater number of tributaries. The Ganges 

 and the Brahmapootra have perhaps become partially con- 

 fluent in the same delta within the historical, or at least 



junction 



Mississippi 



been known, if America had not been so recently discovered. 

 The union of the Tigris and the Euphrates must undoubtedly 

 have been one of the modern geographical changes of our 

 earth, for Sir Henry Rawlinson informs me (1853) that the 

 delta of those rivers has advanced two miles in the last sixty 

 years, and is supposed to have encroached about forty miles 

 upon the Gulf of Persia in the course of the last twenty-five 



centuries. 

 Wheni 



rivers, having many mouths, converge 



-P 



d thro 





> 



arm* 



l 





• 



tompo 



then* 

 tit m<3 



the relat 

 : flnc 



in: 

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