APPENDIX G. 



249 



of Family Facilities. This will now be briefly described again. 

 Each kinsman can be described in two ways, either by letters or by 

 a number. In ordinary cases both the letter and number are 

 intended to be used simultaneously, thus FF.8. means the Father's 

 Father of the person described, though either FF or 8, standing by 

 themselves, would have the same meaning. The double nomen- 

 clature has great practical advantages. It is a check against mis- 

 take and makes reference and orderly arrangement easy. 



As regards the letters, F stands for Father and M for Mother, 

 whenever no letter succeeds them ; otherwise they stand for Father's 

 and for Mother's respectively. Thus F is Father; FM is Father's 

 Mother ; FMF is Father's Mother's Father. 



As regards the principle upon which the numbers are assigned, 

 arithmeticians will understand me when I say that it is in accord- 

 ance with the binary system of notation, which runs parallel to the 

 binary distribution of the successive ranks of ancestry, as two 

 parents, four grandparents, eight great-grandparents, and so on. 

 The "subject" of the pedigree is of generation ; that of his 

 parents, of generation 1 ; that of his grandparents, of generation 2, &c. 

 This is clearly shown in the following table : — • 



Kinship. 



Order 



of 

 Genera- 

 tion. 



Numerical Values 



in Binary Notation. 



in Decimal Nota- 

 tion. 



Child 







1 



1 





Parents 



1 



10 



11 



2 



3 





Gr. Par, 



2 



100 



101 



110 



111 



4 



8 

 9 



5 



10 

 11 



6 



12 



13 



7 



14 

 15 





G. Gr. Par. 



3 



1000 

 1001 



1010 

 1011 



1100 

 1100 



1110 



llll x 



All the male ancestry are thus described by even numbers and the 

 female ancestry by odd ones. They run as follows : — ■ 



