In message , at 22:28:39 on Wed, 6
Jan 2016, Clive D. W. Feather remarked:

And was the Cam ever tidal, say in Newton's time, at Cambridge ?
It's an awfully long way from the sea, so no.

Irrelevant.

It is relevant because tidal effects require large amounts of water to
move twice a day, and the further they have to go the less likely it is
to happen.

Although as Denver Sluice predates Newton, that's probably a simpler
answer to the specific question asked.

The Great Ouse is tidal up to Brownshill Staunch, about 4 km upstream
of Earith. Though curiously (to the uninitiated) it's non-tidal
downstream of Earith.

That'll be Hermitage Lock, hiding in plain sight:

https://goo.gl/maps/YKR6xFHVrYq

....for the Great Ouse via Ely. The Environment Agency deems that the
Bedford Rivers are also part of the Great Ouse though, so that bit of
the downstream will be tidal. But it's very hard to see any tidal
component to the levels recorded here, which is about halfway to the sea
from Earith:

http://apps.environment-agency.gov.u...s/120730.aspx?
stationId=6245

As opposed to the next measuring point north of the

http://apps.environment-agency.gov.u...s/120731.aspx?
stationId=6290
--
Roland Perry