SPRINGS AS A GEOGRAPHIC INFLUENCE 



5°9 



and texture of the formation, also because of its subjacency to horizons 

 that carry water freely. 



In the Logan formation, I have mapped thirty houses with springs. 

 There is doubt concerning a few of these, an indefmiteness occasioned 

 by the absence of contacts. The Logan sediments suffered erosion con- 

 temporaneously with Pottsville sedimentation; furthermore, the Logan, 

 in comparison with its contact formations, the Black Hand and the 

 Sharon, weathers easily, producing gentle slopes. These two condi- 

 tions make it doubtful about the exact horizon of a spring near either 

 the top or the base of the Logan. 



Sawed Shingles and a Few Boards are used in lengthening the Years of Service of 



this Rough-hewn Log Spring house. 



Slightly less than seventeen per cent, of the houses with springs 

 are found in the Sharon. The areal extent of all the exposed forma- 

 tions diminishes vertically, hence the number and the volume of the 

 springs decrease; the value of the land for farming also decreases with 

 altitude. A further fact concerning the springs of the Sharon is their 

 content of iron, making them less desirable than springs in either of the 

 lower formations. 



