204 HENSCHEL'S TURBINE. 



thumb of the left hand, and water poured with the right hand in 

 the cylinder. When the finger is withdrawn, and the water i 

 allowed to flow through the aperture into a vessel which has bee: 

 placed ready for its reception, the screw will rotate, and the rotatio 

 may be maintained for some time if the cylinder is kept full 

 constantly pouring in water at the top. 



This apparatus becomes a good approximate model of a HensclieV 

 Turbine a kind of water-wheel recently much used on a large 

 for imparting motion to machinery if another wheel is placed in a 

 fixed position above the moveable one, but having the blades in- 

 clined in a direction opposite to that of the blades of the moveab 

 wheel. The fixed wheel may be made of a circular disc of metal, 

 large as just to fit into the narrower part of the cylinder, and bavin 

 a hole in the middle which must be at least l mm wider than th 

 thickness of the spindle. In cutting the blades these will slight! 

 bend by the pressure of the shears, but as their inclination is the sa 

 as in the moveable wheel, the blades must first be all straighten 

 with the wooden mallet, and then bent in the other direction wi 

 the flat pliers ; if this is done without previously hammering the di 

 flat, the latter is likely to be spoiled. Two brass wires, about 1 

 thick, are soldered with one end to two opposite blades of the sere 

 with the other to the cross-strip at the top ; the wires should hav 

 a length which permits the two screws to be as near as possible 

 one another without touching. Fig. 146 G shows the upper portio 

 of the whole apparatus. By using two moveable screws, o 

 without and the other with a fixed screw, it will at once be observ 

 that the latter increases the velocity of rotation considerably : th 

 blades of the fixed screw direct the current of water in such 

 manner as to produce a much greater effect upon the moveab 

 blades than the current would have upon them if it were simply 

 flow in a vertical direction. 



When a liquid flows rather rapidly through a tub* 

 which becomes suddenly wider at one part, certain phe- 

 nomena may be observed which will be considered aftei 

 the effects of atmospheric pressure have been studied. 



23. Molecular Phenomena. Adhesion. Capillarity, 

 Solubility. Diffusion. Endosmose. Some of the 

 phenomena which depend on the action of molecular 

 forces upon liquids, especially the tension of liqui< 

 surfaces, have been already studied in articles 3 and 4, 



