MARYLAND GEOLOGICAL SURVEY 133 



is much more apt to be impure, although in many places it is used 

 exclusively without any apparent injurious effects. 



ARTESLA.N Wells. — As good water in sufficient quantity can be ob- 

 tained almost everywhere in the county at moderate depths few attempts 

 have been made to obtain artesian water. Borings that have been made, 

 however, show that artesian water underlies practically the entire county. 

 Flowing wells have been secured on the low-lying land bordering Chesa- 

 peake Bay and the Patuxent River, but it is very doubtful whether they 

 can be secured at any point in the county with an elevation exceeding 

 20 feet above sea level. The water obtained in the artesian wells usually 

 contains some mineral matter in solution but not sufficient to interfere 

 with its use for most purposes. Free from surface contamination, it is 

 the most healthful water of the region. 



There seems to be two distinct water horizons that furnish the supply 

 in the artesian wells thus far bored. One of these is found in the upper 

 portion of the Cretaceous, probably within the Magothy formation, while 

 the other is located near the base of the Calvert formation. 



The Magothy ( ?) Horizon. — The only artesian well in the county 

 that derives its water from the upper Cretaceous is the 295-foot well at 

 Chesapeake Beach. The water is of good quality and yields about six 

 gallons per minute. This seems to be the same horizon which has been 

 penetrated by the flowing wells at Upper Marlboro at a depth of about 

 225 feet. 



In the northern part of the county the Magothy horizon is the only 

 one that lies near enough to the surface to be reached at moderate depths. 

 Since all the Coastal Plain formations clip to the southeast beneath pro- 

 gressively younger deposits, presumably the artesian water-bearing hori- 

 zons of the Potomac formations which supply the water for many 

 artesian wells near Washington and Baltimore, underlie Calvert County. 

 They are, however, so deeply buried that only the demand for an unusu- 

 ally large supply'of water would warrant seeking artesian water from 

 these strata in Calvert County, since the Magothy horizon seems to be 

 sufficient for present needs. In the central and southern portions of the 

 county where another artesian water-bearing horizon lies nearer the 



