"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.