OF THE UNITED STATES. 415 



gravel must be penetrated, before the Gneiss rock, which as- 

 certains the formation, is found. 



Beginning at the bay of Penobscot (to the northward and 

 eastward of which most probably the primitive descends through 

 a gradual transition to the secondary, and thus into the Inde- 

 pendent coal formation, round in such abundance in Nova 

 Scotia;) and proceeding south, the sea coast is primitive to Bos- 

 ton, where the transition covers it as far as Rhode-Island. 



ALLUVIAL FORMATION. 



On the south east side of Long-Island the alluvial begins, 

 occupying more than the half of that island; its western and 

 northern boundaries are marked by a line passing near Amboy, 

 Trenton, Philadelphia, Baltimore, Washington, Fredericksburg, 

 Richmond, and Petersburg in Virginia, a little to the westward 

 of Halifax, Smithfield, Aversborough and Parker's Ford on Pe- 

 dee river, in North Carolina, west of Cambden near Columbia, 

 Augusta on the Savannah river, Rocky Landing on the Oco- 

 nee river, Fort Hawkins "on the Oakmulgee river, Hawkins- 

 town on Flint river, and running west, a little southerly, across 

 the Chatahouchee, Alabama and Tombigby rivers, it joins the 

 great alluvial bason of the Mississippi a little below the Natchez. 



The ocean marks the eastern and southern limits of this ex- 

 tensive alluvial formation, above the level of which it rises con- 

 siderably in the southern States, and fails to near the level of 

 the sea, as it approaches the north. 



Tide water in all the rivers from the Mississippi to the Roan- 

 oke stops at a distance from thirty to one hundred and twenty 

 miles short of the western limits of the alluvial; from the Ap- 

 pomatox to the Delaware, the tide penetrates through the allu- 

 vial, and is only stopped by the primitive rid^e. 



The Hudson is the only river in the United States where the 

 tide passes through the alluvial, primitive, transition, and into 

 the secondary, in all the northern and eastern rivers, the tide 

 runs a small distance into the primitive formation. 



Through the whole of this alluvial formation, considerable 

 deposits of shells are found ; and a bank of shell limestone be- 



i i 



