I9I5-] 



RODDY— CONCRETIONS IN STREAMS. 



257 



Table Showing Relation Between the Salinity of Streams and the 

 Presence of Calcium Carbonate Concretions. 



Stream or Spring-. 



Salinity, 

 Parts in One 



Million. 



Nature of Salinity 

 (Chiefly). 



Concretions 



Present in 



Stream. 



1. Little Conestoga 



2. Little Conestoga 



3. Little Conestoga 



4. Branch Run, tributary to 



Little Conestoga 



5. Big Conestoga 



6. Big Conestoga 



7. Big Conestoga 



8. Duing's Run, tributary to 



Big Conestoga 



9. Pequea Creek 



10. Donegal Run 



11. Nissley's Dam in Donegal 



Run, further upstream 

 than 10 



12. Donegal Run near source. . . 



13. Bellaire Branch of Donegal 



Run 



14. Little Chickies 



15. Big Chickies 



16. Big Chickies farther up- 



stream 



Feb. 5 

 March 

 April 



April 

 Feb. 

 March 

 April 



April 

 April 

 April 



April 



April 



April 

 April 

 April 



April 



330 

 300 

 365 



91 

 152 

 100 

 150 



195 

 195 



404 



400 



230 



208 

 170 

 171 



174 



CaH2(C03 



Abundant 



None 



None 



None 



None but 

 many gas- 

 teropods 



None 

 None 

 Abundant 



Many but 



small 

 None 

 None except 



near mouth 

 None 

 None 



None 



Further Notes on Concretionary Formations in Streams. 

 Since writing the above I have been fortunate enough to find 

 a new locality for concretions. Knowing that Donegal Township, 

 Lancaster County, comprised a notably large area of Cambro- 

 Ordovician limestones, I judged that its streams would be favorable 

 to the growth of calcareous concretions through the agency of blue 

 green algae. Search on April 25, in Donegal Creek, revealed these 

 objects in greater abundance than in the Little Conestoga. One 

 meadow of fully 12 acres bordering the stream about one mile 

 northeast of Marietta was found to be underlain with a bed of con- 

 cretions not less than a foot in average thickness throughout its 

 entire extent. And this was under a soil cover of more than a foot 

 in depth that had, apparently, resulted from the weathering and 

 disintegration of the same objects. The great flood deposits of con- 

 cretions in this and neighboring meadows were paralleled by large 

 quantities in the stream itself, fully one fifth of the stones in some 



