No. 2.] 



TRIAD SYSTEMS— WHITE, COLE, CUMMINGS. 



87 



The tables of intcrlacings for the remaining seven apparently duplicate pairs of systems 

 are adjoined below and establish the noucongrucncy of the two systems in each pair. 



Table of interlacings for the system IIC. 



The system IID contains no column similar to the column d of IIC, therefore IIC and 



III) are noncongruent. 



Table of interlacings for the system HE. 



The system IVA contains no column similar to the column a of HE, hence HE and IVA 



are noncongruent. 



Table of interlacings for the system IVB. 



Table of interlacings for the system VD. 



No column in VD is similar to the column a of IVB, hence IVB and VD are noncongruent. 



Table of interlacings for the system VA. 



