ECOLOGICAL STUDY OF DRY RUN 117 



anything interesting as to the distribution of the fishes. A rather 

 large tributary which appears near the north end of the "Diagonal" 

 changes the character of the stream considerably — particularly as to 

 size. This tributary rises in a rather extensive boggy area to the 

 west of this end of the road. 



Probably the most interesting stretch of stream is that from the 

 end of the "Diagonal" to the quarry shown in figure 20. For the 



Fig. 16. — Characteristic view of Dry Run as it nears outcropping of lime. tone. 



most part, the most marked change is in the nature of the bottom. 

 The brook changes from a stream of uniform depth and rate of cur- 

 rent flow to a stream of pools and rapids. Wherever the water 

 flows rapidly instead of the mud bottom we find gravel and sand. 



Fig. 17. — Large sink hole in limestone in which water disappears completely 

 during dry weather. 



