MARYLAND GEOLOGICAL SURVEY i i 



certain seasons they are frequented by wild waterfowl in such num- 

 bers that they have long been known to sportsmen as among the 

 finest hunting grounds in the country. The water in the estuaries 

 is fresh or very slightly brackish, and ebbs and flows with the tide. 

 There is seldom any distinct current to be noticed and such as is 

 seen is due to the incoming or outgoing tide and appears to be nearly 

 as strong when moving upstream as when moving in the opposite 

 direction. 



The Potomac River. — The Potomac Kiver is the most important 

 stream to be mentioned in connection with the drainage of Prince 

 George's County. It forms about half of the western boundary of 

 the County and receives, through its numerous tributaries the drain- 

 age of about two-thirds of the area. The Potomac is an estuary up 

 as far as Georgetown and is navigable almost to the head of tide 

 water. Steamboats carrying freight and passengers ply between 

 Washington and Chesapeake Bay ports, particularly N"orfolk and 

 Baltimore, though the modern high-draft war and ocean-going ves- 

 sels cannot reach the city, and thus the I^avy Yard at Washington 

 ceases to fulfil the expectations of the founders of the capital. 



The estuary of the Potomac is from one-half to one mile in width 

 along the borders of the County and gradually increases in width to 

 about 13 miles at its mouth. The current is very slight and with the 

 rising tide the water flows upstream. Almost the only rocks pres- 

 ent are occasional loose boulders which have been washed out of tlie 

 Pleistocene deposits along the shores or have been transported from 

 the Piedmont Plateau by floating ice. The banks are usually low 

 though occasional bluff's of considerable height border the river. 

 In this region the bluff on which Fort Washington stands is the 

 highest and rises with very steep slopes over 100 feet above the 

 water. 



At Georgetown the crystalline rocks pass beneath the water and 

 this marks the head of tide water. Westward the stream gradient 

 is much steeper, the river is narrower, the current is rapid, the bed 

 of the stream is filled with boulders or ledges of rock, and the enclos- 

 ing walls are of hard rock rising, in many places, almost perpen- 

 dicularly from the water's ed^'e. 



