166 SEC. 5. MOLECULAR PHYSICS. 



615. Electrical Apparatus belonging to Air Pump. 



Vertical cylinder electrical machine with two leather rubbers. 

 The apparatus is so constructed that the cylinder may be enclosed 

 in a large glass receiver, which can be exhausted. 



The Council of King's College, London. 



616. Large Air Pump, arranged for producing the ordinary 

 vacuum or a dry vacuum of a millimetre of mercury, and also for 

 producing ice. M. Carre, Paris. 



616a. Small Air Pump, also capable of being transformed 

 at will into a eompressionpuinp. M. Carre,, Paris. 



617. Apparatus for producing ice by vacuum and sulphuric 

 acid. M. Carre, Paris. 



619. Hydraulic Press of Copper and Glass (for demon- 

 stration). Luizard, Paris. 



620. Apparatus for Compression. Luizard, Paris. 



62Oa. Model of an Air Compressor, which may also be 

 used as a water meter. M. Eugene Bourdon, Paris. 



621. Air Pump for Double Exhaustion (Babinet's prin- 

 ciple). . Luizard, Paris. 



62 la. Model of Pneumatic Machine. 



M. Loiseau, jun., Paris. 



627. Pick's Spring Manometer. Weber, Wurzburg. 



63O. Air Pump, made by Spencer & Sons, Dublin. 



Prof. W. F. Barrett. 



This air pump has no valves between the barrels and the receiver, hence 

 it is free from regurgitations of air, and is capable of making a vacuum nearly 

 equal to that obtained by means of Sprengel's air pump. The ends of the 

 pistons and barrels are conical, and, when they are in contact, no cavities 

 remain. All the air in the barrels is therefore expelled at each stroke of the 

 piston ; the effect is the same when it is highly rarefied. The horizontal 

 portions of the pump admit of the barrel being brought into close connexion 

 with the plate, and leaves the valves accessible for cleaning or repairs. 



63Oa. Single Barrel Air Pump. James How and Co. 



630b. Air-pump on Babinet's system. Dr. Stone. 



680a. Improved Portable Spireometer. E. Cetii fy Co. 



