133 THE ECONOMIC RESOURCES OF CALVERT COUNTY 



cerns, but because of the gentle slope of all except the smallest streams 

 the amount of water-power developed is very slight. 



Springs. — The nature of the topography of the region with many 

 stream-valleys cut almost to sea level combined with the gentle dip of the 

 different beds of vaiying permeability afford excellent conditions for the 

 development of springs. The ground water sinking through the porous 

 Pleistocene deposits until the less porous beds of the Miocene are en- 

 countered, flows along the contact until it is tapped by some valley 

 slope where it issues as a line of seepage or as a spring. A large per- 

 centage of the ground water is not checked at the contact of the Pleisto- 

 cene and Miocene but passes downward through the sandy layers of the 

 latter formation until its further progress is checked by more argillaceous 

 beds along which it flows until the layer outcrops at the surface. The 

 more deep-seated springs of the latter sort which penetrate Miocene beds 

 are apt to be purer than the shallow springs and furnish an unfailing 

 supply of excellent water. In addition to the increased danger of con- 

 tamination in the shallower springs, they are very apt to fail in dry 

 weather. 



While the spring water is sometimes charged with iron derived in the 

 main from the Pleistocene deposits, it is as a rule remarkably free from 

 mineral matter of all kinds. 



Dug Wells. — Except on the top of narrow divides between deep valleys, 

 the ground water level lies near the surface and abundance of water can 

 be obtained from dug wells of shallow depth. On the narrow divides, 

 however, the water table in the dry months of the year lies only a little 

 above sea level, thus necessitating the sinking of wells almost to that 

 plane in order to obtain a permanent supply of water. The highest 

 divides in the county rise to an elevation of about 180 feet and in a few 

 instances it has been necessary to sink wells to almost that depth to 

 secure plenty of water during all seasons of the year. On the broad, 

 low-lying flats bordering the Patuxent Eiver, on the other hand, it is 

 seldom that the wells exceed 20 feet in depth and sometimes tlic water 

 rises to the surface. In general the water in these most shallov/ wells 



