158 SEC. 5. MOLECULAR PHYSICS. 



II. AIR PUMPS AND PNEUMATIC APPARATUS. 



597. Air Pump, by Otto von Guericke, with stand. 



Professor Dr. Lepsius, Berlin. 



606. Otto von Guericke's Air Pump. 



" Collegium Carolinum" Polytechnic School at Bruns- 

 wick, Professor Dr. If. Weber. 



The earliest trustworthy information respecting Otto von Guericke's original 

 apparatus is contained in a list of the physico-chemical apparatus of the 

 Collegium Carolinum, at Brunswick, of the year 1816. In this list it is stated 

 that this apparatus was obtained from the legacy left by Aulic Councillor 

 .Beireis, in Helmstedt. According to a special ordinance of His High- 

 ness Frederick Wilhelm, Duke of Brunswick, dated 8th October 1814, the 

 collection of physical, mathematical, and astronomical instruments acquired 

 from the legacy left by Beireis, physician in ordinary, at Helmstedt, was 

 exhibited in the rooms, and by a later ordinance dated 9th March 1815 incor- 

 porated with the collections of the ducal Collegium Carolinum. The air-pump has 

 been preserved unaltered, with the exception of the lever and the piston attached 

 to it, the former having been replaced by a new one of the same construction, 

 and the latter by a wooden one, in the year 1864. The pump has been described 

 and faithfully represented by a drawing in a work published by Otto von 

 Guericke, entitled " Ottonis de Guericke Experimenta nova (ut vocantur) 

 Magdeburgica de vacuo spatio Ainstelodani," 1672, cap. IV. p. 75, Tab. VI., 

 in which work he also (p. 122) successfully refuted the assertion of Augustus 

 Hauptmannus, doctor of medicine, in his " Berg-be-deneken, anno 1658, 

 Lipsiae," " that it would not be possible to either angel or devil to 

 bring about a vacuum." This work is in the possession of the ducal library, 

 at Wolfenbiittel. But, previous to this air-pump, Otto von Guericke had con- 

 structed one more simple, consisting of only one cylinder and a piston, which 

 is said to be in the library at Berlin (see No. 597). The difficulty, however, 

 connected with the motion of the piston, the resistance of the air against the 

 free piston being so great that it required two strong men to pull it out re- 

 peatedly, p. 75, induced him to contrive their second improved construction. 

 The receiver stand at present in use was unknown to Otto von Guericke. 

 In order to produce a vacuum, he employed a hollow copper ball with stop- 

 cock,* which was placed in the axis of the barrel. It was exhausted, and 

 screwed on to other vessels, which, by the repetition of the process, were also 

 exhausted. The pail of tin-plate attached to the lower end of the barrel, 

 as well as the copper bowl fastened to the upper end of the barrel, were filled 

 with water or oil, in order to effect a greater tightness. 



607. Two large Magdeburg Hemispheres of copper. 



Professor Dr. H. Weber, Brunswick. 



The two large hemispheres of copper are those of which Otto von Guericke 

 states, in page 104, Tab. XI., that after their exhaustion they could not be 

 separated by the united strength of 16 horses. They have a diameter, as 

 mentioned in the work alluded to above, of nearly f Magdeburg ells, or, 

 according to a second more exact statement, 0'67 Magdeburg ells. 



* This ball (page 88, Tab. VIII.), as well as a pair of still larger Magdeburg hemi- 

 spheres, nearly an ell, Magdeburg measure, in diameter, which 24 horses had not the 

 power to separate (page 105), and, lastly, a copper boiler with inserted piston, which, 

 when the air below the same was withdrawn, 50 men were not able to lift or to pull up 

 (page 109, Tab. XIV.), are likewise enumerated in the list, but are no longer to be 

 found. 



