ID: 
2404
Maker's Name: 
John J Griffin
Where made: 
England
Dimensions: 
13 × 13 × 30 cm

These were used to demonstrate that the Earth's atmosphere exerted a force on surrounding objects.

The hemispheres were held together, and air exhausted from the interior.

As the atmosphere exerts about 15lb/sq in force or 100kPa pressure, it requires a large effort to pull the hemispheres apar.t