260 A short Account of Horizontal Water-Wheels. 
A mahogany-wheel or pulley of equal diameter to the wheel is 
fixed on the top of the spindle, and above it one of about 6°5 
inches diameter is fixed, for the purpose of making experiments. 
The water escapes at the bottom quite round the machine. 
Experiments. 
With this model or mill, the foliowing experiments were made. 
When the reservoir was full to above four feet above the cen- 
tre of pressure, or middle point in the cuts, the wheel made 
nearly four revolutions in a second, and, as no weight was then 
suspended, this was its greatest velocity. 
A cord was then fixed to the smaller wheel, and passed over a 
pulley, with a weight suspended, when twelve revolutions of the 
wheel made in 
25 12 50-4 
13 | seconds } 10 J) 96°92 | feet in a 
6 ( raised 8 pariieis, 2h TeeK 210° minute. 
5 6 252° 
Then each weight multiplied by the height to which it was 
raised in a minute gives the momentum ; therefore 
12x 50° 4= 604'8 
10x 96°92= 969:2€ _ 
8x210° =1680: =the momentum. 
6 *252-) =1512- 
- Hence it appears, that the third experiment produced the 
greatest effect, and that the wheel then made twelve revolutions 
in six seconds, or two in one second, and therefore it moved with 
nearly half of its greatest velocity. Consequently, when the 
wheel moves with nearly half of its greatest velocity, it works to 
the greatest advantage, supposing the third experiment to be 
the maximum, ’ 
Diameter or Size of the Wheel. 
This wheel may be made of any diameter that may be required 
for making a given number of revolutions in a given time. 
Velocity. 
The wheel may move with any velocity whatever that can be 
obtained from the fall. 
Mr. Banks, at page 105 of his Treatise on Mills, by taking a 
mean of the experiments made by six different authors, for the 
purpose of finding with what velocity water will issue from a fall 
of a given depth, gives 5:4 x square root of the depth = velo- 
city of the water. 
But according to these experiments, 6 comes much nearer 
than 5:4, and also agrees exactly with the experiments made by 
Banks himself; and as, in these experiments, it gives nearly the 
velocity 
