Rising Temperatures

Well actually as they rise they fall.  This clever little device uses wizard magic to tell the temperature in the house.  As it get hotter the little globes fall to the bottom of the column leaving the current temperature at the bottom of the stack.  It does have a proper name, it is called a Galileo thermometer.
 
As it was only at 20oC I decided to light the wood burner for Mrs F, half an hour later we were at 22oC.  Boy do I know how to treat a lady right.