I was going through all my old photos on google and forgot about these. I was working on the foundations of the 2 new bridges, and whilst bridge A was being excavated for the new foundations some of the old ones where still intact.
I don't know what these are, maybe someone else does, but it looks like the base of the swing bridge.
Incidentally, they were under some other foundations as well.
These were taken on the Wallasey side.

This foundation was what was on top of the circular foundation. Now this one I have no clue about.

All the bridges were hydraulic swing bridges before the Bascule bridges replaced them around 1930.

There were/are also lock gates under many of the bridges.

Slightly off topic, but I came across evidence of a the locks on the Weaver navigation canal being operated by water turbines - Pelton wheels I was later told.

I've not bothered to look into it further than a quick Google, but seems to confirm this. How they worked is probably carefully documented somewhere. Has anyone taken teh trouble to dig it out?