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

[Philip Saddleton]

CC Decision (E)A.1.g

 > A method has 'palindromic' symmetry if it is the same method when 
rung backwards, that is when the order of the changes is inverted. A 
method has 'double' symmetry if it is the same method when reversed, 
that is when the places within each change are inverted. A method has 
'rotational' symmetry if it is the same method when reversed and rung 
backwards.

A method that has any two of these will necessarily have the third. Ann 
seems to be assuming that Double refers to the 'rotational' symmetry 
above, when it in fact it is (unsurprisingly) the 'double' symmetry that 
matters. Since most methods have 'palindromic' symmetry, the distinction 
is not often necessary.

The only case where the Decisions prescribe that Double has to be part 
of the name is (E)D.2.e

 > If a non-Little Plain method with double symmetry and either one 
plain hunting hunt bell or two or more principal hunts, all of which are 
coursing, has the same number of leads in the plain course as the 
corresponding method with no internal places below the hunt bell or 
principal hunts, they shall have the same name but with the prefixes 
"Double" and "Single" respectively.

As Eddie points out, this is the case for Double Cambridge Cyclic. It 
does not preclude Ann from naming her method Double whatever.

Philip

edward martin said  on 26/01/2010 09:22:
> 2010/1/23 Graham John <graham at changeringing.co.uk>:
>> 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
>>
> 
> Thanks for your speedy reply; however I think the key point to what
> she was saying was more a matter of semantics :
> "Don't we need two words for these two kinds of doubleness?"
> 
> In 18th century ringing books, if a method was referred to as ‘Double’
> it meant that places were made both sides of the treble. This is no
> longer the case. It is my understanding that the requirement to call a
> method ‘Single’ only applies to methods that are purely plain hunting
> (i.e. have no internal places) below the hunt bell. With this
> definition of a single method there's always a 1-1 relationship
> between a double method and a single method (you can take any
> seven-lead plain major method and perhaps construct a single method by
> removing all the internal places from under the hunt bell, and
> conversely any method which has no internal places below the hunt
> bells can be doubled up). So there is no ambiguity about the members
> of the single/double pair. It therefore follows  that in a ‘Double’
> method, (where the PN of the second half lead is a mirror reflection
> of that of the first half lead) because the place notation above the
> treble is mirrored with place notation below the treble, the work off
> the back is the mirror image of work off the front; Now, this is not
> case with Double Cambridge Cyclic Bob Major/Minor /Royal so, why is it
> called ‘Double’ ?
> 
> To try to understand this, using Don Morrison’s fantastic ‘Method
> Information’, I typed in the notation of what ought to be Single
> Cambridge Cyclic Bob Minor/Major/Royal and got ‘unnamed’. The LHs were
> cyclic & I suppose that the methods just have not been rung &
> therefore not officially named, but when/if they are then they will
> have to be named ‘Single Cambridge Cyclic’.
> 
> This still does not answer the missus’s question which seems to me
> that there are conflicting uses of the word ‘Double’ when used in the
> name of a method. Am I right in thinking that a lead block whose PN is
> mirror reflected about the half lead, from rounds cannot produce a
> cyclic LH, If so then, since we can have both Single & Double Cyclic
> methods, isn’t this a specific use of the word ‘Double’ and wouldn’t
> Double Cambridge Cyclic be better named Cambridge Double Cyclic ?
> 
>