s in most cases less than the price of a good
farm horse_--the $200 kind--not counting labor of installation.

It is the purpose of these chapters to awaken the farmer to the
possibilities of such small water-power as he or his community may
possess; to show that the generating of electricity is a very simple
operation, and that the maintenance and care of such a plant is within
the mechanical ability of any American farmer or farm boy; and to show
that electricity itself is far from being the dangerous death-dealing
"fluid" of popular imagination. Electricity must be studied; and then
it becomes an obedient, tireless servant. During the past decade or
two, mathematical wizards have studied electricity, explored its
atoms, reduced it to simple arithmetic--and although they cannot yet
tell us _why_ it is generated, they tell us _how_. It is with this
simple arithmetic, and the necessary manual operations that we have to
do here.

CHAPTER III

HOW TO MEASURE WATER-POWER

What is a horsepower?--How the Carthaginians manufactured
horsepower--All that goes up must come down--How the sun lifts
water up for us to use--Water the ideal power for generating
electricity--The weir--Table for estimating flow of streams, with a
weir--Another method of measuring--Figuring water horsepower--The
size of the wheel--What head is required--Quantity of water
necessary.

If a man were off in the woods and needed a horsepower of energy to
work for him, he could generate it by lifting 550 pounds of stone or
wood, or whatnot, one foot off the ground, and letting it fall back in
the space of one second. As a man possesses capacity for work equal to
one-fifth horsepower, it would take him five seconds to do the work of
lifting the weight up that the weight itself accomplished in falling
down. All that goes up must come down; and by a nice balance of
physical laws, a falling body hits the ground with precisely the same
force as is required to lift it to the height from which it falls.

The Carthaginians, and other ancients (who were deep in the woods as
regards mechanical knowledge) had their slaves carry huge stones to
the top of the city wall; and the stones were placed in convenient
positions to be tipped over on the heads of any besieging army that
happened along. Thus by concentrating the energy of many slaves in one
batch of stones, the warriors of that day were enabled to deliver
"horsepowe