FORTY-FIRST ANNUAL REPORT. 



147 



P F P 



'/ 



P F 



F F 



P P 



Square system. 



P F P F P F P 



Square system with fillers. 



P F P F P F P 



F P F P F P F 



P F P F P F P 



F P F P F P F 



P F P F P F P 



F P F P F P F 



P P 



Quiucunx .system. 



P F P F P F P 



Qiiincunx system with fillers. 



P 



P P P 



Hexagonal system. 



P 



P F P F P F P 1< 

 FFFFFF FF 



FPFPFPFP 

 FFFFFFFF 



PFPFPFPF 

 FFFFFFFF 



FPFPFPFP 



Hexagonal system with fillers. 



