Farms and Villages. 
47 
freight, acting on the incline, would communicate motion to 
the driving-drum and to any machinery connected to it. 
I w as informed that these horse-mills are very much used in 
homesteads, and that they answer very well, and do not injure 
the horses. They are compact, and may readily be fixed in 
a barn or stable.* 
Rivers very commonly afford the power requisite for raising 
a portion of their own waters to any required height. Where 
the flow in the river is at all times ample, the required supply 
must be first determined, and then the quantity of water neces- 
sary to work the motor must be considered. 
Small water-wheels, which can be used with very low falls, and 
even as stream-wheels in rapid rivers, may be estimated to do, 
with their pumps, about 40 per cent, duty, that is to say, the 
weight of water pumped per minute multiplied by the total 
height raised, including the resistance of friction in the pipe, 
will be 40 per cent, of the weight of water falling multiplied 
by the height of the fall. Thus, suppose that a house, using 
500 gallons per day, has to be supplied by a water-wheel 
intended to work about 10 hours a day with a fall of 1 foot 
■6 inches. The water lifted would be a little under 1 gallon 
per minute. The rising pipe might be 1-inch diameter ; our 
diagram tells us that the hydraulic inclination would be 1 in 
200, and if the pipe were a mile long, the head of friction would 
be 26 feet. The absolute height to which the water would have 
to be raised is, say, 150 feet, making in all 176 feet. 
10 lbs. of water x 176 feet = '40 X lbs. water expended 
X li feet : therefore the water expended would be "^^ ^ "^^^ 
^ ' / -4 X li 
= 2933 lbs., or 293 gallons per minute. 
If a spot in the stream can be found with a few yards of 
tolerably even current and uniform cross section, the volume 
flowing down can be ascertained by observing the distance 
which floats cast into the middle of the stream travel in — sa}', 
one minute. The average velocity is found to be about 80 per 
cent, of the velocity in the centre of the stream, and the quan- 
tity flowing down will be found by multiplying the average 
depth of the water by the width at the surface, by the observed 
velocity, and by '80. 
Thus, suppose a stream is 4 feet wide at the water surface, 
and the depth of water measured in four places across the stream 
is found to be 4 inches, 6 inches, 10 inches, and 8 inches, the aver- 
age depth will be 7 inches, and the cross section 4 feet X feet 
* In vol. xiv. of the ' Journal,' page 47. will be found an illustration of the 
manner of ■working three throw pumps by means of horse-gear. 
