Our readers from years ago may remember Derby's previous incident with a Galileo thermometer. Mum was ready to take one of his lives. You can see what he did back here.
Now mum has two of these Galileo thermometers. Her own, which is glass and hangs in the doorway where we cannot get at it.
Then there is a smaller and plastic version that sits back where the first one did. However this is plastic, so it should be something Derby can't break. This was Grampie's Galileo.
One of the colder mornings mum was watching and caught the one little bulb going down as the room got warmer.
Here are a few more close pics, mum's glass one and the little bulbs.