What is this strange chimney in Stone?

On my way back from Christchurch in Stone this morning I noticed a chimney with large circular holes in it towards the top.

A quick internet search yielded nothing useful; does anyone know what it is?

I forgot to mention yesterday how high the Trent was at Shugborough. This is the packhorse bridge; I was in danger of getting wet feet taking this photo. The ground was boggy and there was other evidence of the water level having been even higher.

We moved on to Barlaston, checking out the canalside Plume of Feathers for a meal but deciding to eat on board instead. The pub's offering was a limited menu for Fathers' Day.

This afternoon it rained. I thought we'd had enough of the stuff in the last few days to last the summer, but apparently not.

FMC Dove, with shiny brasses, came past earlier.

Stoke-on-Trent tomorrow, where we will make a last-ditch attempt to locate our missing postal votes. Curiously, Ally and Ben seem to have received Jan's ballot papers despite them already having been sent elsewhere. Must be a duplicate. We really don't know what's going on, but there's a chance Jan, at least, could get to vote in the referendum.