A case full of receipts for artists' supplies and scientific equipment--glass and earthenware retorts, imploding bottles, Magdeburg hemispheres
, a bottle of yellow powder--conveys an experimental disposition she must have shared with Blake.
The theme was the power of pressure and the club members learnt how to make their own air cannon from a tin, looked at alternative boomerangs and experimented with Magdeburg hemispheres
(They were called Magdeburg hemispheres
because Guericke was mayor of Magdeburg.) When the hemispheres were put together and the air within them evacuated, air pressure held them together even though teams of horses were attached to the separate hemispheres, straining to their utmost in opposite directions.