GUERICKE, ga're-ke, OTTO VON ( 1602-86 ) . A celebrated physicist, known chiefly by his dis coveries regarding the nature and effects of air. He was born at Magdeburg, and studied in Ger many and Holland, subsequently traveling in England and France, and becoming later an engineer in the army of Gustavus Adolphus. In 1640 he was made Burgomaster of Magdeburg, and became greatly interested in the philosophi cal discussions dyer the vacuum which were in progress. The experiments of Galileo and Pas cal on the weight of air led Guericke to at tempt the creation of a vacuum. His first ex periment was made by filling a stout barrel with water and ,then pumping out the water, but it was found that no sooner was a vacuum produced in the barrel than the air forced its way through. He next took a globe of copper provided with a stop-cock, and having an opening at the bottom, into which a pump was fitted. To his astonish ment he found that the pump extracted the air quite as well as the water, and when he opened the cock the air rushed in with a whistling noise.
This, the first air-pump, was invented about 1650. (See Aia-Pultp.) Guericke's invention soon became famous, and in 1654 he was summoned to the presence of the Emperor Ferdinand III. of Germany at Ratisbon, at which time he made the famous experiment commonly known as the `Magdeburg Hemispheres' (q.v.). Guericke's Dc Vacuo Spatio, a work in seven books, written in 1663, was published in 1672, and the third book, which contains an account of his experiments, was translated into German and published in Ost wald's Klassiker, No. 59 (Leipzig, 1854). Gue ricke's name is also associated with the begin nings of scientific investigation in the field of electricity. In his experiments he applied fric tion to a sphere of sulphur.