to Ground Water along Coasts. 293 



salty in summer. The drilled well of Robert Mitchell, at 

 Sachem Head, Guilford, is on a narrow point 50 feet 

 from high tide on two sides. It is about 50 feet deep. 

 The well was drilled for the supply of a summer cottage, 

 but the water became so salty that the well was entirely 

 abandoned in 1919. The following quantities of chloride, 

 in parts per million, were found in four samples examined 

 in 1919: May 19, 49; June 16, 94; Aug. 4, 50; 

 Nov. 28, 31. 



The water of the Anderson drilled well on Mulberry 

 Point, Guilford, becomes salty whenever it is used. 

 Nevertheless it is used in summer, as it is the only supply 

 available. The quantity of water used does not vary 

 greatly from day to day, and the results given below 

 represent mainly natural seasonal variations in salinity. 

 Some analyses made in 1919 showed the following quanti- 

 ties of chloride, in parts per million : June 16, 37 ; Julv 

 12, 290; July 17, 516; July 20, 446; Aug. 4, 355. 



The results indicate a seasonal variation in salinity 

 much like that in the Beattie well, though the great 

 increase between June 16 and July 12 may be largely due 

 to the drain upon the well. The mounting salinity early 

 in July shows the effect of a sharp drought and subse- 

 quent decreases closely follow rains on July 16 and 

 August 1. 



.Such remarkable fluctuations in salinity in ground 

 water must be confined to small islands and isolated 

 points Avhere the total quantity of fresh ground water is 

 very small and where the increment from rains reaches 

 the sea quickly. It is quite possible, however, that at 

 some places on mainland coasts seasonal fluctuations have 

 an appreciable effect on the zone between salt and fresh 

 ground water in which contamination by sea water occurs 

 and may cause this zone to progress slightly farther 

 inland in summer. The evident influence of temperature 

 also suggests that in warm climates contamination is 

 relatively greater than in cooler regions with a like 

 amount of rainfall. 



Influence of tides on ground water. 



The water surface in wells near the sea is sometimes 

 affected by tides, but the writer's observations indicate 



