McGee — Gulf of Mexico as a measure of Tsostasy. 181 



The qualitative kind of direct data are well exemplified at 

 the head of the Bay of Bengal with the adjacent Sanderbands, 

 the depositing ground of two of the most potent rivers of the 

 globe (Ganges and Brahmaputra), where the rate of subsidence 

 — shown by the Indian geologists to- have reached over 400 

 feet in recent geologic times — has not been measured, yet is 

 proved to be rapid by the coastal configuration, by the estuaries 

 through which the rivers embouch, and by the immense natu- 

 ral levees flanking the rivers and their distributaries and 

 bounding broad intervening flats, or "jhils"; they are exem- 

 plified again at the mouths of the Amazon and la Plata, which 

 together carry the degradation products of the greater part of 

 the South American continent, and which embouch into vast 

 estuaries after dividing into networks of levee-flanked dis- 

 tributaries insulating extensive marshes ; they are exemplified 

 also about the mouth of the Indus, once supposed to be an 

 area of uplift but now known to be subsiding, where the 

 larger distributaries are estuarine and where the interstream 

 flats are vast salines annually flooded and silt-mantled by fresh 

 waters, yet always so delicately adjusted to tide level as to be 

 flooded and salt-mantled by sea waters during each annual 

 monsoon ; they are apparently well exemplified again about 

 the northern end of Caspian sea and in the delta plains of the 

 Yolga and Ural, as well as about Aral sea and in the broader 

 delta plains of its far-reaching affluents; they are exemplified 

 also on the northern and western shores of Black sea, and still 

 more notably about the Sea of Azof, which together receive 

 the drainage of a third of Europe ; they are exemplified, par- 

 ticularly the estuaries and anastomosing levee-flanked distribu- 

 taries, on the western shore of Iiwang-hai (China sea or Yellow 

 sea) about the mouths of the muddy rivers draining the 

 eastern Himalayas and the loess-mantled plateaus of eastern 

 Thibet and western China ; they are strikingly exemplified at 

 the northwestern extremity of Adriatic sea about the mouth 

 of the levee-lifted Po, perhaps the most energetic river of the 

 world in proportion to its size ; and they are exemplified more 

 notably than elsewhere on the globe about the shores of the 

 Gulf of Mexico, the depositing ground of rivers degrading a 

 fourth of the North American continent. These and other 

 notable examples are summarized in the accompanying table, 

 which is graphically depicted in figure 1 (p. 183). 



On reviewing these examples yielding direct yet only quali- 

 tative data concerning the relation between deposition and 

 subsidence, it appears that the data are of unlike value : The 

 most extensive degradation tract on the globe is that of the 

 Amazon, but the Amazonian detritus is partly spread over a 

 vast flood plain lying at base-level, partly dropped in an exten- 



