"John Cartmell" wrote in message
...
In article ,
Bob Mannix wrote:

"John Cartmell" wrote in message
...
In article ,
Dave Page wrote:
The Natural Philosopher wrote:
Lobster wrote:

When topping up old insulation (Rockwool) it's normal and more
effective to lay the second layer perpendicular to the first.

I think you mean 'orthogonal'

Perpendicular is walls... ;-)

I understood what Lobster meant, and feel that "perpendicular" was
quite
appropriate. After all, laying insulation foam vertically wouldn't
make
sense.

'Perpendicular' without the sense of vertical makes no sense at all.
What
would it be hanging (-pend-) from?

Yes it does. It only implies vertical in some of its meanings
(architecture,
physical landscape) and not in others (maths and the conjunction of two
lines or planes).

AFAIK it should only be used in maths & drawing where it's used to
represent a
physical verticality.

Oh no, definitely not - two lines in maths/geometry perpendicular to each
other are usually representing no physical reality at all but are always
described as perpendicular

Where you are describing a physical (3 or more
dimensions) situation 'perpendicular' cannot mean horizontal.

It cannot *mean* horizontal per se, I agree, but could be used to describe
things which form lines at right angles in some arbitrary plane (which might
be horizontal) by considering them merely as geometric concepts. If the
information being conveyed included information on verticality then
perpendicular would clearly mean vertical.


A quote from Round the World in Eighty Days:

"It was supplied with two rows of seats, perpendicular to the direction
of
the train on either side of an aisle which conducted to the front and
rear
platforms."

The translator made an error.

That one's for a rainy day, I fear, not having a French copy to hand )


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)