[r-t] Interesting observation

Mark Davies mark at snowtiger.net
Mon Oct 17 22:16:04 UTC 2005

Philip Earis writes,

> In any major method with regular (plain bob) leadheads, call a
> single 5ths.  Now if you call a single at any one of the 7 subsequent
> leads, it will take you into one of the cyclic courses

This is something to do with the symmetry between the 2nd and 8th as the
discontinuities of the cyclic leadhead with respect to PB. Any such rule as
you quote would have to work equally with the 2nd. If you consider the
natural coursing order, 8753246, a single on 7 and 3 is the only place such
a call can be made equidistant from both 2 and 8.

The same idea gives you an equivalent rule on 6, I think. Here the
symmetrical choice is to swap 2 and 6 themselves; any further single gives
you a cyclic course. However, it's not sufficient to explain the system, and
it breaks down on ten bells and above (2 swaps not enough to get to a cyclic

Do you get any interesting sets of leadhead groups if you choose a different
pair of bells - 4 and 5, for example?


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