4. “Tarpeia,” tar-peˈya. The daughter of Tarpeius, the governor of the citadel of Rome. She promised to open the gates of the city to the Sabines if they would give her what they carried on their left hands, meaning their gold bracelets. The king consented, and as he entered the gates, to punish her perfidy he threw not only his bracelet, but his shield upon her. His soldiers followed his example, and she was crushed to death. She was buried in the capitol, which from her has been called the Tarpeian Rock. 5. “Haliotis,” hal-i-ōˈtis. A genus of gasteropods with a shell resembling the human ear. The gasteropods are a class of univalve mollusks, like the snail. 6. “Skate.” A kind of shark. A name given to several species of fish having a rhomboidal body. 7. “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. 8. “Otto von Güricke,” fon gāˈrik-eh. (1602-1686.) A celebrated German physicist. He invented the air-pump and made the famous experiment with the Magdeburg hemispheres. 9. “Tower of Pisa.” The round marble belfry called “The Leaning Tower” because it deviates about fourteen feet from the perpendicular. It is 180 feet high, and consists of seven stories divided by rows of columns, and surmounted by a flat roof and an open gallery commanding a splendid view of the surrounding country. It was built in the twelfth century by a German architect, Wilhelm of Innsbruck. 10. “Mariotte,” Mä-ri-ŏtˈ. A French philosopher of the seventeenth century. He possessed an extraordinary power of drawing conclusions from experiment. He made a thorough investigation of the subject of the conduction of water, and calculated the strength necessary for pipes under different circumstances. 11. “Air-gun.” An instrument resembling a musket. By means of a condenser the air is forced into a metallic globe which is attached to the musket nearly opposite the trigger. 12. “Torricellian Vacuum.” To produce this vacuum a small quantity of pure mercury is placed in the tube and boiled for some time. It is then allowed to cool and a further quantity, previously warmed, added, which is boiled, and so on until the tube is quite full; in this manner the moisture and the air which adhere to the sides of the tube pass off with the mercurial vapor. 13. “Mont-golˈfi-er.” There were two brothers of this name, Etienne and Joseph, distinguished as the inventors of the first kind of balloons. They were both received as members of the French Academy. They lived in the latter part of the eighteenth century.