182 If c Gee — Gulf of Mexico as a measure of fsostasy. 



sive estuary, and partly cast into the sea to be widely distrib- 

 uted by exceptionally powerful oceanic currents ; and, more- 

 over, this vast river is comparatively little affected by seasonal 

 freshets such as multiply the efficiency of extra tropical streams. 



Principal Degradation Tracts of the World (exclusive of Africa, Australia and 



Northern Lands) with the Correlative Deposition Tracts. 



o' Degradation Tracts. Deposition Tracts. 



fc Rivers. Areas. "Water Bodies. Approximate Areas. 



Amazon 



Mississippi, 



Kio Grande, el 



Yang-tse-Kiang 



Hwarjg-ho. 



La Plata 



Danube 



Don 



Dnieper 



Dniester 



Other rivers 



Volga 



Ural 



Syr Daria 



Amu Daria 



Ganges } 

 Brahmaputra \ 

 Indus 



al. \ '" 



sq. 771. 



730,000 



715,000 



sq. m. 



. 2,010,000* Atlantic ? 



.l,804,737f Gulf of Mexico. (N. half) 27 ? 7,592^ 



312,0001 

 225,000 j 

 225,000 y 

 30,000 I 

 200,OOOJ 

 530.000 / 

 110,000 f 

 316.000 j 

 260,000 \ 



10 St. Lawrence 



[ Rhine 87,000] 



,, j Elbe 56,000 [ 



] Weser 17.000 f 



[Other rivers ... 10,000 J 



f Connecticut ") 



, „j Hudson ! 



j Delaware 



[_ Susquehanna, et al. j 



j Po 40,000 \ 



j Adige, et al. 30,000 ) " 



.1,445,000* 

 .1,175,000* 



992,000* 



640,000* 

 576,000* 



. 575.000* 



. 415,000* 

 _ 395,000* 



Hwang-hai ( W. pt.) ? 200,000§ 



Atlantic ..?... 



j Black sea ) 

 j Azof <j 



172,50011 



Caspian .. (N. half) 90,000| 



Aral 24,000«[ 



Bay of Bengal (N T . part) ? 100,000§ 

 Arabian gulf __(E. part) ? 80,000§ 

 Gulf of St. Lawrence .. ?50,000§ 



L3 



f LoDg Island sound "] 



I New York bay 

 83.000f ■{ Raritan bay ^?5,000f 



I Delaware bay | 



[_ Chesapeake bay, et al J 

 70,000* Adriatic (N. part) ? 7,000§ 



Ratio. 



6£: I 



11:1 



? 



5*:1 



7 : 1 



24: 1 



5f: 1 



5: 1 



8: 1 



170,000* Xorth sea ? I5,000§ Llj: 1 



16*: 1 



10: 1 



The second degradation area in extent is that of the Mississippi, 

 the Rio Grande, and their weaker neighbors, whose deposits 

 not only fall into the nearly enclosed Gulf of Mexico but, by 

 reason of the prevailing currents, are confined to its northern 

 fraction. A portion of this degradation area is indeed sub- 

 arid and only a small portion is mountainous ; yet in general 

 degradation is rapid — toward the Rocky Mountains because of 



* Reduced to statute miles from A. Keith Johnson's " Physical Atlas of Natural 

 Phenomena,'' 1856, pis. 16, 17. 



f Computed by means of the planimeter from the United States Geological Sur- 

 vey " 9-sheet" base map of the United States, by John B. Torbert. 



\ Computed by John B. Torbert. 



§ Estimated. 



||Encyclopedia Brittanica, 9th edition. 



^[ Appleton's American Encyclopedia. 



