265 



and found to be lower than that deduced by Smeaton from 

 his experiments, which the author presumes arises from the 

 better construction of apparatus, and better form of bucket 

 used in the present case. 



The author then ascertains, by another train of experi- 

 ments on both wheels, the value of the circular conduit or 

 race, and finds, in round numbers, that there is an economy 

 of labouring force, amounting to from eight to eleven per cent, 

 of the power of the fall, obtained by its use. This conduit 

 acts by retaining the water in the buckets at the lower por- 

 tion of the loaded arc. The velocity of a water-wheel work- 

 ing thus, he finds may vary through a greater range without 

 a material loss of power than when working naked, and that 

 a steady motion is also continued to a much lower velocity. 



The author arrives at the following practical conclusions : 



1st. When the depth of water in the reservoir is inva- 

 riable, the diameter of the water-wheel should never be 

 gi-eater than the entire height of the fall, less so much of it 

 as may be requisite to give the water a proper velocity on 

 entering the buckets. 



2nd. When the depth of water in the reservoir varies 

 considerably and unavoidably in depth, an advantage may 

 be obtained by applying a larger wheel dependent upon the 

 extenl offluctuaiion and the ratio in time that the water is at 

 its highest and lowest levels during a given prolonged period ; 

 if this be a ratio of equality in time there will be no advan- 

 tage, and hence in practice the cases will be rare where any 

 advantage will be obtained. 



3rd. If the level of the water in the reservoir never fall 

 below the mean depth of the reservoir, when at the highest 

 and lowest, and the average depth be between an eighth and 

 a tenth of the height of the fall, then the average labour- 

 ing force of the large wheel will be greater than that of the 

 small one, and it will of course increase this advantage at 

 periods of increased depth of reservoir. 



