[r-t] Fwd: "double" cambridge?

[edward martin]

On 23 January 2010 19:51, Graham John <graham at changeringing.co.uk> wrote:
> Eddie sent some questions re method symmetry from Ann
>
>> ... not symmetrical in the classical way around the treble
>
> Eddie - You obviously haven't been keeping Ann abreast with historical
> postings from this list, or the musings of PJE. Try the page below for
> starters.
>
> http://www.cantabgold.net/users/pje24/sym.html
>
> Graham

"Glide symmetry (skew symmetry)
First used in 1752, it has become popular recently due to its use in
cyclic methods."

Could someone please give me details of what was used in 1752? and how
do we know?
I cannot find reference in any of the 18th century books to which I have access

mew