The Tracing of Underground Waters. 53 



percolate through soil, gravel, sand, or detritus. Its appearance will 

 be the longer delayed, the finer the material through which the water 

 passes. 



In reply to Dr. Moir, the author mentioned that he had succeeded 

 in establishing, by means of fluorescein, the connection between two 

 surface waters four miles apart, although only about an ounce oi 

 fluorescein was available at the time. 



