Mercury relay

[djrm]

Then you have the most ingenious time delay tilt switches used in clocks etc. that had a restriction to slow the reverse flow of the mercury, very clever.

Here is a brief video of my Gents bellringer mercury delay in operation: https://youtube.com/shorts/OPXZ7pls_zU
After being tilted by the 5 minute mechanism then the bell rings until the mercury runs through the constriction into the other chamber.
   
David