already over sixty.

"Our social structure, to be brief, is based on science, or the
conservation of energy, as the Greek philosophers predicted. It
was known to them that a certain amount of power would produce
only a certain amount of work--that is, the weight of a clock in
descending or a spring in uncoiling returns theoretically the
amount of work expended in raising or coiling it, and in no
possible way can it do more. In practice, on account of
friction, etc., we know it does less. This law, being
invariable, of course limits us, as it did Archimedes and
Pythagoras; we have simply utilized sources of power that their
clumsy workmen allowed to escape. Of the four principal
sources--food, fuel, wind, and tide--including harnessed
waterfalls, the last two do by far the most work. Much of the
electrical energy in every thunderstorm is also captured and
condensed in our capacious storage batteries, as natural hygeia
in the form of rain was and is still caught in our country
cisterns. Every exposed place is crowned by a cluster of huge
windmills that lift water to some pond or reservoir placed as
high as possible. Every stiff breeze, therefore, raises millions
of tons of water which operate hydraulic turbines as required.
Incidentally these storage reservoirs, by increasing the surface
exposed to evaporation and the consequent rainfall, have a very
beneficial effect on the dry regions in the interior of the
continent, and in some cases have almost superseded irrigation.
The windmill and dynamo thus utilize bleak mountain-tops that,
till their discovery, seemed to be but indifferent successes in
Dame Nature's domain. The electricity generated by these, in
connection with that obtained by waterfalls, tidal dynamos,