GUERICKE, OTTO, or OTEIO, a very eminent German experimental philoso pher in the seventeenth century, who, with Torricelli, Pascal, and Boyle, greatly contributed to explain the various proper ties of the air and their effects, was born in the year 1602, and died, at Hamburgh, in the year 1686. He was councellor to the Elector of Brandenburg ; and burgo master, or consul, of Magdeburg ; but his memory derives greater honour front his philosophical discoveries, than front the civil dignities to which he was rais ed. To him is to be attributed the inven tion of the air-pump, for though Mr. Boyle had, about the same time, made some approaches towards a similar disco very, yet he ingenuously acknowledged, in a letter to his nephew, Lord Dungar von, that the information which he re ceived from Schottus's " Mechanica Hy draulico Pneumatica," published in 1657, in which was an account of Guericke's ex periments, first enabled him to bring his design to any thing like maturity. Gue ricke was also the inventor of the two brass hemispheres, to illustrate the pres sure of the air, which, being applied to each other, and the air exhausted, resist ed the force of sixteen horses to draw them asunder. He likewise invented an
instrument to show the variations in the state of the atmosphere, consisting of a tube, in which was a little image of glass, that descended in rainy or stormy wea ther, and rose again when the weather became fine and serene. This last ma chine fell into disuse on the invention of the barometer, and especially after the improvements made in that instru ment by Iluygens and Amontons. By consulting his tube, Guericke would fre quently foretel approaching storms ; whence the ignorant populace gave him the character of a sorcerer. In this opi nion of him they were confirmed, by a thunder storm discharging itself one day upon his house, and shivering to pieces several machines, of which he had made use in his experiments. That event they considered to be an unequivocal in dication of the anger of Heaven, and a just punishment inflicted upon him for his impiety. He was the author of several treatises in natural philosophy, the prin cipal of which is entitled " Experimenta Magdeburgica," 1672, folio, and contains his experiments on a vacuum.