Now, suppose that an inventor succeeds, as well he may, in making
a machine which would go into a watch-case, yet complete in all
its parts, able to fly around the room. It may carry a button, but
nothing heavier. Elated by his success, he makes one on the same
model twice as large in every dimension. The parts of the first,
which are one inch in length, he increases to two inches. Every
part is twice as long, twice as broad, and twice as thick. The
result is that his machine is eight times as heavy as before. But
the sustaining surface is only four times as great. As compared
with the smaller machine, its ratio of effectiveness is reduced to
one-half. It may carry two or three buttons, but will not carry
over four, because the total weight, machine plus buttons, can
only be quadrupled, and if he more than quadruples the weight of
the machine, he must less than quadruple that of the load. How
many such enlargements must he make before his machine will cease
to sustain itself, before it will fall as an inert mass when we
seek to make it fly through the air? Is there any size at which it
will be able to support a human being? We may well hesitate before
we answer this question in the affirmative.
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