OF PNEUMATIC APPARATUS. 191 



'2229. Madgeburg Hemispheres, consisting of two hollow half globes of brass, ground 

 and fitted to each other so that their rims when touching are air-tight ; the 

 lower one has a stop-cock attached. This apparatus demonstrates the pressure 

 of the air which nearly equals 151bs. for every square inch, of surface, 

 11s. 6d., 15s. 6d., and 126 



2230. SET OF Two MILLS, consisting of two separate axles, with four thin vanes of 

 equal length, breadth, and weight. One set of vanes has its planes at right 

 angles to its axle ; the planes of the other set are parallel to it 1 12 6 to 



200 



2232. GUINEA AND FEATHEB APPAEATUS, showing that the resistance of air diminishes 



the velocity of falling bodies more or less according to their densities, whilst 

 in vacuo both fall at the same rate ; one fall, 9s. ; two falls, 12s. ; three falls 



17 6 



2233. Artificial Fountain, produced by the elasticity of air. It consists of a vessel 



to be partly filled, with a tube reaching nearly to the bottom. When under 

 the receiver, and the air exhausted, the spring of the confined air on the water 

 forces it up in a pleasing jet, 5s. 6d., 7s. 6d., and . . 10 6 



2234 SINGLE TRANSIT PLATE, with jet pipe and stop-cock; a tall receiver being placed 

 upon the plate and the air removed from it, if the tube be immersed in water 

 and the stop-cock turned, the water will be forced up the pipe, thus forming 

 a beautiful fountain within the receiver . . . 086 



2235. DOUBLE TRANSFEREE, on stand with fountain jet and 2 glass receivers 220 



2236. BACCHUS EXPERIMENT, illustrating the elasticity of air . 110 



2237. Glass Model of the Diving Bell, loaded at the bottom sufficiently to sink it. 



A condensing syringe is furnished for supplying fresh portions of air under 

 the bell, likewise a stop-cock as an outlet for impure air. Painted wooden 

 fig ures are supplied, and a burning spirit lamp may be placed under the 

 bell . 150 



2238. GLASS FLASKS, with brass cap and stop-cock, illustrating the influence of 



diminished pressure in facilitating ebullition ; they may also be employed for 

 weighing air or any other gaseous fluid . . . 076 



:2239. BLADDER AND WEIGHT in frame. If this apparatus be placed under a receiver, 

 and the air removed, the air contained in the bladder will expand and raise 

 the leaden weight, thus illustrating the elasticity of air 7s. 6d. to 12 6 



2240. Expansion and Compression Bottles, to illustrate the pressure and expansive 

 power of air, each . . . . . . 013 



2242. VALVES for ditto, each Is. ; cage for ditto . . . 030 



2243. FRUIT AND TAPER STAND, each . . . . 020 



2244. FLINT AND STEEL APPARATUS, for proving that sparks cannot exist with- 



out air . . . . . . . 18 6 



2245. BEAM AND STAND, with cork or globe . . . . 10 



2246. COPPEE BOTTLE, beam and stand, for weighing air and gases . 220 



2247. FILTEEING CUP, for mercurial shower, with receiver . 5 6 to 10 6 



2248. PLATE, with wooden disc, for proving the porosity of vegetables 066 



