CONCLUSIONS 



349 



southern part of the region may have occurred without bringing the 

 beaches perceptil)ly out of level. The tilting that Gilbert finds occurred 

 between 1858 and 1896 may have gone on for the last 700 years (7 times 

 5 inches equals 35 inches), and yet the beach would not be three feet out 

 of level in a hundred miles today. Can any one, from a study of these 

 beaches, assert that they are not deformed to that amount ? Would seven 

 centuries suffice to give the rivers a distinct tendency toward the south? 

 There are no criteria at hand for an answer; but the supposition that 

 they might does not seem unreasonable. 



It does not seem to the author that sufficient evidence has been gath- 

 ered to say that the rivers support the view. The most that he would 

 claim is that their evidence is in accordance with such a view as far as it 

 goes. 



From this point of view streams may be classified according to the 

 angle that their course makes with the direction south 27 degrees west. 

 If a tilting in that direction is affecting the flow of streams, it should 

 hasten those flowing south 27 degrees west, causing them to deepen their 

 channels, as has happened to the North branch of the Eouge. Those 

 flowing north 27 degrees east it should check, making their course swampy 

 and abounding in pools, as is believed to have happened to the Concord 

 and upper Charles, in Massachusetts, from this same cause. Those flow- 

 ing east 27 degrees south or west 27 degrees north should attack their 

 banks to right and left respectively. Intermediate directions should 

 show intermediate effects. Morainal and shoreline guidance is likely to 

 render such criteria at times hard to apply. 



XXX— Bull. Geol. Soc. Am., Vol. 18, 1906 



