Footnote 69
Supp. Prop., §43.  Here versa (in M.) is certainly miswritten for recta, as in L.  See fig. 18, Plate VI.  Here Eb = E'b' = 12; b'c' = 1, bc = 2.  Hence E'B = 1/12 BC, EB = 2/12 BC, whence EE' = 1/12 BC.  Or again, if bc become = 3, 4, 5 &c., successively, whilst b'c' remains = 1, then EE' is successively = 2/12 or 1/6, 3/12 or ¼, 5/12, &c.  Afterwards, add in the height of E.