COMMON THINGS PUMPS. 



o. Animal power may be applied to this method of raising 

 [ water by such an arrangement as is represented in fig. 4. This is 



Fi<r. 4. 



the method generally used in France by the market gardeners, in 

 the environs of large towns, to raise water for irrigation. Two 

 pulleys are established side by side, over the well, at such a dis- 

 tance asunder that two buckets or barrels suspended from them 

 may pass each other as one ascends and the other descends, with- 

 out mutual collision or obstruction. The rope supporting one 

 bucket, after passing over one of these pulleys, is carried two or 

 three times round a large vertical drum erected near the well, 

 and then passing over the other pulley is let down into the well 

 with the other bucket attached to it. 



The semicircular handles to which the rope is attached, are con- 

 nected with the barrels, not at the edge of the mouth, but at two 

 points in their sides, a little above their middle point, so that when 

 filled they will maintain themselves steadily in the vertical position, 

 but when empty they will easily be turned upon their sides by mere 

 contact with the surface of the water so as to fill themselves, when 

 let down empty. 



A horse or ox yoked to a lever of considerable length, projecting 

 from the vertical shaft, turns it, and with it the drum, and con- 

 tinues to go round in the same direction, until one barrel is raised to 

 the mouth of the well and the other is plunged in the water below 

 and filled, the contents of this barrel being discharged into a reser- 

 voir or vessel destined to receive it. The animal is then yoked 

 in the other direction, and again travels round until the other 

 barrel is raised, and that which was just discharged let down. 



6. It is evident that in this and all similar arrangements the 

 weight of the rope on the whole balances itself ; for although it 

 preponderates against the power when the full barrel begins to 

 180 



