MARYLAND GEOLOGICAL SURVEY 131 



Not all of the diatomaceous earth of the region is valuable, some con- 

 taining an excessive amount of sand. At Lj'ons Creek wharf, in Calvert 

 County, it is quite pure and has been worked tor a number of years Ijy 

 the Maryland Silicate Company. Because of the limited demand for 

 it and the considerable number of States in which diatomaceous earth 

 is found it is improbable that the industry in southern ilaryland will 

 ever reach very large proportions. 



The Water Eesources. 



The availnlile water resources of St. Mary's County include the surface 

 streams, natural springs, and the dug or driven wells. In the absence of 

 large towns or great industries where large amounts of water are re- 

 quired, the streams have not been utilized for water-supply purposes. 

 In fact, it is doubtful if they could ever be depended upon for potable 

 water because of the large amount of vegetation which they contain 

 during the summer months arid the liability to contamination from the 

 run off of the adjoining cultivated lands. In some instances dams have 

 been constructed and the power utilized by small manufacturing con- 

 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 unfailmg 

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

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