On Thu, 18 Aug 2005, Martin Underwood wrote:

"Tom Anderson" wrote in message
h.li...
On Thu, 18 Aug 2005, David Spiro wrote:

Another interesting difference is the almost complete lack of
underground line in south London - here, the suburban surface rail
network was very well-developed early on (and extensive urbanisation
was later than in the north, i think), so the need for tubes never
arose. I don't know if there's a a parallel in New York - are there any
boroughs with surface rail lines rather than subways?

I thought one of the reasons that there are very few tube lines south of
the Thames is that the geology is different and doesn't lend itself to
tunnelling - except around Crystal Palace where the Sydenham tunnels are
through rock that is easier to tunnel through.

Yes, i've heard that too, but i think it's an urban myth. We've gone over
it here before; google groups might be able to turn up more info.

tom

--
On two occasions I have been asked [by members of Parliament], 'Pray, Mr.
Babbage, if you put into the machine wrong figures, will the right answers
come out?' I am not able rightly to apprehend the kind of confusion of
ideas that could provoke such a question. -- Charles Babbage