ELISHA MITCHELL SCIENTIFIC SOCIETY. 2i 



rivers flowing east or west have their banks worn away in 

 the same manner as those flowing north or south. \ 

 bod>' at rest upon the earth, and free to move in any direc- 

 tion upon it, ''is maintained in equilibrium by attraction 

 directed towards the earth's center, and centrifugal force 

 directed away from the axis. If the centrifugal force 

 ceased, the body would evidently move towards the nearest 

 pole as down a hill. From the poles to the equator m.ay 

 therefore be regarded as uphill — bodies free to move being 

 prevented from going down towards the poles by centrifu- 

 gal force. Suppose now a body to move from f^est to east — 

 that is, in the same direction as the earth revolves; the 

 centrifugal force of the body is increased, and there is a 

 tendency to move uphill towards the equator. If the 

 motion be from east to west, the centrifugal force is dimin- 

 ished and the body tends towards the pole. In each case 

 the tendency is towards the right in the northern hemi- 

 sphere and towards the left in the southern."* 



Admitting the sufficiency of the terrestrial rotation for 

 the deflection of streams, we must look for our examples to 

 those regions where the strata are essentially horizontal and 

 horizontally homogeneous. McGee, in his paper on the 

 geology of the Chesapeake Bay, says: "It may be noted 

 in passing that, throughout its gorge, the Susquehanna 

 River hugs its left shore the more closely, and apropos to 

 the hypothesis of the dextral deflection of rivers by terres- 

 trial rotation (commouly known in Europe as Baer's law), 

 specifically applied by Kerr to the water-ways of the Mid- 

 dle Atlantic slope, and recently discussed in more general 

 terms by Gilbert, Davis, Hendricks, Bains, and others, it 

 may be mentioned that the difi'erent water-ways of the Mid- 

 dle Atlantic slope are not only inconsistent in their behav- 

 ior at and above the fall-line, but in many cases the same 

 stream has not behaved uniformly since the excavation of 

 its gorge was initiated, "f 



* A C. Bains, in a paper read before the Philosophical Institute of Canterbury, New 

 Zealand, October 4, 1877. 

 t Seventh annual report of the Director of the United States Geological Survey, p. 554. 



