By Hamish Johnston

Last week I promised readers a genuine mystery – and here it is. Do you know what this piece of apparatus was used for?

It currently resides in the McPherson Collection of physics instruments at McGill University in Montreal and its purpose has long puzzled curator Jean Barrette – who I spoke to when I was in Canada recently.

The device looks like it is designed for bench-top use and Barrette believes that it was used to study gases. Inside the cylindrical section with the half-moon window there is another small cylindrical part that can move. The small cylindrical extension to the right of the main component is an electrode input to bring high voltage inside the chamber.

“Any idea on the purpose of the instrument would be greatly appreciated,” said Barrette.

There must be a physicsworld.com reader out there who knows what this is. Please let Jean and I know by leaving a comment below.