Mr Bayliss's Amazing Autovent

We visited Lacock today and during a little rain shower we sheltered in a hothouse in the garden of the Abbey.

The gardeners don't have time to maintain the temperature here so Mr Bayliss invented this contraption.

When the greenhouse gets hot, the wax in the narrow tube at the bottom expands pushing a piston in the wider tube up. This in turn moves a weight which then opens the roof vents above it.

When the temperature cools down, the wax shrinks, the piston and weight fall and the vents close.

Clever Mr Bayliss!