Note 7 — HOME STUDIES IN CHEMISTRY AND PHYSICS.
Reading edition
“Magdeburg Hemispheres.” They are two hollow hemispheres generally made of brass or copper, with edges accurately fitted to each other, and one of them provided with a stop cock. When the edges are pressed tightly together and the globe thus formed is exhausted of air through the cock, the hemispheres are held together with such force that it is with great difficulty they can be pulled apart.