162 SEC. O. MOLECULAK PHYSICS. 



laboratory. i! The other and greatest misfortune was that, having undertaken 

 to shoot the same with steam as with pOM'der, he might have provided a 

 weapon of great destructive power. The machine prepared for that pur- 

 pose, however, exploded, not only demolishing a great part of the labora- 

 tory, and mortally wounding several men (one among whom had his jaw- 

 bone carried away), but Landgrave Karl himself, who is a very curious 

 lord, intent upon seeing and examining everything minutely, might have 

 been hit, and have lost his life, had not His Highness been accidentally de- 

 tained by other affairs and come to the laboratory later. On this occasion 

 Papin was dismissed from his service." 



614. Air Pump with two Barrels. The first pump of the 

 kind ever constructed. It is an exhausting and a condensing 

 pump, and was made for King George III. in 1761. 



The Council of King \s College, London. 



618. The Abbe NoUet's Air Pump. 



Conservatoire des Arts et Metiers, Paris. 



586. Hand Pump, Regnault's System improved. 



Geneva Association for the Construction of Scientific In- 

 struments. 



Exhausting and forcing hand pump. The hand pump, constantly used in 

 laboratories, has now attained a satisfactory practical shape, from which not 

 much deviation is possible. Its general proportions are determined by the 

 consideration of how best use can be made of muscular power, with simpli- 

 city and facility of carriage of the apparatus. Silken valves, as being too 

 perishable, are excluded and replaced by cones of metal and leather. All the 

 movable parts, piston and valves, are equally accessible. ' Three cocks effect 

 the complete cutting off of all communication between the pump and the 

 exhaust and the compression receivers, as well as restore direct com- 

 munication, either between both or one of these and the atmosphere. If 

 rarefaction is required in the compressing vessel, or vice versa, Without dis- 

 turbing the tubes of communication, the relative position of the valves must 

 be inverted, which may be done in a few minutes, or else a change cock 

 must be joined to the pump. 



For effecting all communication between the pump and its receivers, a 

 screw flush joint is always used, which is very safe, and can be fitted to 

 tubes made of india-rubber, copper, or lead. This avoids the deterioration of 

 the india-rubber, which is unavoidable on account of the constant action of 

 fastening the joints, especially as it is rarely that a thoroughly air-tight joint 

 can be made with india-rubber alone. 



588. SprengePs Mercury Pump. 



Prof. Dr. R. A. Mees, Director of the Physical Labora- 

 tory of the University of Groningen. 



This instrument differs from all others (1) in the numerous curvatures of 

 the tube through which the mercury falls. These augment the exhausting 

 power of the pump, while the air bubbles, which are carried away with the 

 mercury, and which, when near vacuum, are so minute that they remain 

 hanging on the walls of the tubes before coming down, assemble in the curva- 

 tures, until their size is so far augmented that they are carried away by the 

 falling mercury. (2) The instrument is provided with a peculiar stop-cock 

 with two perforations, whereby the flowing of the mercury is regulated and 



