On 06/01/2022 17:03, Nick Odell wrote:
> Completely without any evidence whatsoever, my money would initially
> be on the Greenwich time ball. Intended for shipping, I'd bet that the
> London skyline was so different in those days that it could be seen
> from plenty of other places too.
There's a chuffing great hill in the way, with a rather large cathedral
on top, then another one just North of the Tower of London, so the only
terminus you could see the ball from might have been London Bridge. The
site of the Greenwich observatory was chosen partly due to it being so
far from the bright lights of London, and partly for its very good
visibility from the river. It was also on land owned by the guy that
set it up.
The ball was the official primary reference for everyone, in the same
way the BBC and others now use the pips. Even the GPS satellite clocks
and the pips on the radio are secondary sources. The one o'clock ball's
timing was checked using a sextant or similar at the observatory to
check the highest point of the sun's traverse at noon.
Excavated ovine, all these
> developments came in such a short time of each other (passenger
> railways, 1820s; time ball 1830s; electric telegraph 1840s) that by
> 1850 or thereabouts I doubt if it would have made much difference
> anyway. When did universal railway time begin?
I'm not sure of the dates, but it was introduced after a series of
collisions when it was found that a train had left Bristol on time,
using local solar time for Bristol, then met a train coming from London,
which was running on London solar time, which was about five minutes
ahead of Bristol.. Oops.
It didn't take them long to introduce token block working, which is
still used in some places. Once that became universal, exact train times
became less important.
L.T.C. Rolt's 1955 book "Red for Danger" is a very good reference to the
early dangers of rail travel and how they got round them.