Mr J. G. Stuart on (he Turbine Water-Wheel. 165 



of the common construction, which can only be calculated for 

 the minimum, and allow the overplus to go to waste. 



Such are the general results borne out by Morin's experi- 

 ments in this treatise. Riihlman has also published a very 

 full report on the theory and practical working of the Turbine. 

 I have not seen it, but only extracts from it. From these I 

 find him stating, as the general result, that 70 per cent, of 

 the theoretical power may be depended upon in all cases. As 

 to the choice between turbines and horizontal axle wheels, he 

 says, that where there is a fall of a certain height which may 

 be economized by means of an over shot- wheel, such is to be 

 preferred to the turbine ; for, when carefully arranged, the 

 overshot- wheel economizes more than 70 per cent, of the 

 theoretical power ; but in all cases of high or very low falls, 

 the turbine is to be preferred to all other wheels. He far- 

 ther states, that their universal application, in such circum- 

 stances, can only be retarded by want of foresight or know- 

 ledge of their actual performance. 



In regard to this statement I would fully coincide with it, 

 restricting the preference for the overshot, to falls from 20 to 

 30 feet, in which there is no fear of back-water, and from 

 which a quickly brought-up motion is not required. Below 

 20 feet, the overshot is not economical, and above 30 feet it 

 becomes a very expensive wheel in erection. The overshot- 

 wheel is certainly that, of all tlie engines hitherto in use, 

 which most effectually economizes water-power ; but the tur- 

 bine has two great advantages over it, in being adapted to 

 any fall^ rvhether high or low, and in pertnitting the water to 

 be applied at the same instant to every point of the circumfe- 

 rence. Farther, the turbine will, in general, be less expen- 

 sive in the erection than any other wheel. It is simple in its 

 construction, and little liable to break or go out of order; and, 

 consequently, it will suffer less than any other wheel from 

 ordinary tear and wear. 



I venture to indulge the hope that the Society will accord 

 me some credit for having risked the experiment of intro- 

 ducing this wheel on a large scale ; and I will only add, that 

 if they shall think the matter worthy of being remitted to a 

 Committee, I shall be ready to afford the gentlemen appoint- 



