FIG. 19 MONTHLY AVERAGE COPPER CONCENTRATIONS AT ALL STATIONS. 



THE DENSER SHADING REPRESENTS THE LOWER, SERIES B STATIONS. 

 DURING SOME MONTHS THE VALUES CLOSELY OVERLAP. 



Each radius represents - 150 ppb copper reading 

 from the center to the circumference. 



(CONTROL) 



Each radius is numbered as the hours on a watch and represents that month. 



63 



