VAJ19' : IMPLEUEXT& OF IRRIGATION. Ill 



wheels the lift in this case being only half the diameter. 

 This form is more like the elaborate "Tympan" with its 

 volute formed compartments, which can only be made in 

 thin iron plates. 



As the tara carries water at its circumference its largest 

 diameter rarely exceeds 5 metres for a lift of 3 metres. 

 Larger wheels than that cannot be made stiff enough 



FIG. 56. Tin: TABOO 



without too greatly increasing weight and cost, and the 

 load of water carried at the circumference acts against 

 the motive power with a leverage in proportion to the 

 radius of the wheel. 



The tara is made of very thin wood, and in many small 

 pieces, and it will not last over two seasons. If instead 

 of making the divisions of the compartments at right 

 angles to the plane of the wheel one makes them at an 



