280 J. S. Brown— Relation of Sea Water 



water may be expected in deep wells on the New Haven 

 coast probably does not exceed 500 feet at most places, 

 because of the fact that a few hundred feet below the 

 surface water-bearing fractures in the bedrock are prac- 

 tically absent and there is very little circulation of ground 

 water. The safe ratio of depth of well to distance from 

 the shore is difficult to estimate but is placed at about 

 1 to 1 — that is, a well 100 feet from the high-tide shore 

 line should not be drilled more than 100 feet below sea 

 level if any fresh water has been obtained above that 

 depth. 



On many coasts where geologic conditions are unlike 

 those in Connecticut impervious beds seal out salt water 

 from underlying strata containing fresh water. This is 

 particularly true of coastal plains, such as our Atlantic 

 Coastal Plain, where alternating sedimentary beds of 

 different kinds dip seaward at low angles. This condi- 

 tion is exhibited on a small scale, in New Haven Harbor 

 (see beyond). 



Effect of special topographic and geologic conditions. 



Tidal marshes: — Very few wells are sunk within the 

 limits of tidal marshes, but from such information as was 

 obtained the conclusion seems warranted that most of 

 the tidal marshes contain brackish ground water. As a 

 rule the salinity of this ground water is much less than 

 that of sea water, because the tidal water that overflows 

 the marshes is diluted by fresh water from streams as 

 well as directly by rainfall. In many places the underly- 

 ing ground water is further diluted by ground water from 

 adjacent areas. In the more or less stagnant marshes, 

 such as those of Milford, Madison, and Clinton, which 

 receive but little inflow from streams and are separated 

 from the sea only by low, narrow strips of land, the 

 ground water probably is very saline. They may be com- 

 pared to the sea of Haarlem, in Holland, where salt 

 water rises nearly to the surface. (See p. 286.) In nar- 

 row tidal marshes along river estuaries the ground water 

 is much fresher. 



Bar beaches and spits. — It appears from all the evi- 

 dence obtained that the ground water of bar beaches and 

 spits is salty. Probably the water table sinks so low at 



