NPPR: Commentary Line 137 Lemniscate

[sZ]

Accomplishing a figure-eight in wet sand on a bicycle is a rigorous test of
balance and steering control while changing directions. Stands in stark
contrast to Shade's awkwardness.

Bicycle tracks on wet sand

pheasant tracks pointing back

Sherlock Holmes: reversing shoes

Sherlock Holmes: switching animal shoes in a story which also investigates
the pattern of bicycle tires
(The Adventure at the Priory School)

the Shade shoe mystery stamp/impress on damp turf

quartic = 'of the fourth degree' -> Jack Degree

Lemniscate of Bournoulli (involves Ex and Wye squared)
Lemniscate of Gerone
http://jwilson.coe.uga.edu/Texts.Folder/Lem/Lemniscates.html

The boy was picked up at a quarter past/Eight in New Wye

You scrutinized your wrist: "It's eight fifteen.
[And here time forked.]

The curving arrows of Aeolian wars.
You said that later a quartet of bores,
Two writers and two critics, would debate
The Cause of Poetry on Channel 8.