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

[Richard Smith]

edward martin wrote:

> In 18th century ringing books, if a method was referred to as ‘Double’
> it meant that places were made both sides of the treble.

Can you think of any methods that were called 'Double' but 
that did not have glide symmetry, then?  I'm not aware of 
any.

> This is no longer the case.

I think it is.  If a plain method has glide symmetry (and 
isn't Plain Hunt), then it must have places above and below 
the treble.

RAS