Changes I would make

[Geoff Bannister]

No: HPFGUIDX 177463

--- In HPforGrownups at yahoogroups.com, Random832 <random832 at ...> wrote:
>
> (of spirals, helices, accuracy, and fancy words)
> 
> Geoff Bannister wrote:
> > You still haven't answered my previous question as to why you 
> > would prefer Hermione to speak about  "a characteristic helical 
> > pattern". If she, as the pedantic bookworm that she is, is satisfied 
> > with 'spirals', who are we mere mortals to argue with her?
> > :-)))
> 
> And of course, all this is ignoring the fact that the characteristic 
> pattern could very well be a spiral rather than a helix.

Geoff:
One definition from the Web is: 
"In mathematics, a spiral is a curve which turns around some 
central point or axis, getting progressively closer to or farther 
from it, depending on which way one follows the curve." 

...while a second is: 

"A plane curve traced by a point circling about the center but 
at increasing distances from the centre". As has been stated 
earlier in the thread, it is a TWO-dimensional curve.

So, unless the steam coming from the Amortentia potion which 
Hermione is describing comes off and stays flat just above the 
surface - like the grooves in a gramophone record - which it 
isn't doing, then it is technically a helix but is invariably called 
'spiralling'. 

As I have said already, it is a non-mathematical vernacular usage 
which we are seeing here.