156 PROFESSOR TAIT ON KNOTS. 
(8). (6) and (14) give the scheme 
ACBECFDBEAFDIA 
one form of which is as follows :-— 
(y). From (7) and (12) we have 
ACBECFDAEBFD|A 
which has as one form 
(8). (8) and (15) give 
ACBECADFEBFD|A 
of which one form is 
§ 9. The case of seven intersections is the only other to which I have found 
leisure to apply this method. As I did not see how otherwise to make certain 
that I had got all possible forms, I wrote out all the combinations of seven 
different letters, one from each column (in order) of the scheme— 
O DOR oa. AWB 
D E-PeGye Bec 
E. 2 GAY Bee) 
FEF GyA Bie De E 
G AGB €- Dis Fk 
These I thus found to amount to 579. Then, by the help of an improvised 
arrangement of cardboard, somewhat resembling Napier’s Bones, I rapidly 
struck off six of each equivalent set of 7. Thus 87 forms in all were left, viz., 

