452 CHARLES EMERSON FEET 



the plain 150-170 feet north of Athens, 190-200 feet at Albany, and 

 80 feet near Fort Edward. This channel is now covered by tide- 

 water to a depth varying from 10-25 ^^^t at Albany to 15-50 feet 

 north of Athens. This depth of water is included in the above esti- 

 mates of erosion, from Albany south. 



The tributaries of the Hudson have courses that are as significant 

 as that of the main stream itself. The larger streams and the longer 

 small streams that head in the country beyond the limits of the plain 

 and above the level of the Hudson water body descend in general by 

 rather steep slopes to the plain, cross the plain on gentle gradients and 

 descend abruptly near their mouths to the Hudson (Fig. j6, A). On 



Fig. 16. 



A , profile characteristic of streams tributary to the upper Hudson, or flowing either into the Poultney- 

 Mettawce or Fort Edward Valley, B, profile characteristic of streams crossing the clay plain and flowing 

 into northern Lake Champlain. 



the smaller streams in general this steep slope is not far from the Hud- 

 son, and on the larger streams in general it is less abrupt and is 

 farther back from the Hudson. The courses of these streams like that 

 of the Hudson have been determined with few exceptions by the 

 topography of the old lake- or old sea-floor, and one may picture the 

 streams as extending their courses across this floor following the slope 

 of the land as the Hudson water body receded. To these consequent 

 streams subsequent tributaries have no doubt been added, and to 

 the original consequent character of the stream gradients has been 

 added the steep gradient found at the mouth of so many of the streams. 

 The full explanation of this will be taken up later, but it may be said 

 here that this steep gradient is due to so rapid a cutting down of the 

 valley of the Hudson that the smaller and weaker tributaries were 

 unable to keep pace with it. The reason for this will appear later. 

 In some cases the failure of the tributaries to keep pace with the Hud- 

 son in its downcutting is due partly to the disadvantage of a hard 

 rock-bed, with which the Hudson did not have to contend. 



