indications that man will become immortal upon earth than that he
will have four eyes and four hands, or that trees will grow
horizontally instead of perpendicularly.

It will be said, perhaps, that many discoveries have already
taken place in the world that were totally unforeseen and
unexpected. This I grant to be true; but if a person had
predicted these discoveries without being guided by any analogies
or indications from past facts, he would deserve the name of seer
or prophet, but not of philosopher. The wonder that some of our
modern discoveries would excite in the savage inhabitants of
Europe in the times of Theseus and Achilles, proves but little.
Persons almost entirely unacquainted with the powers of a machine
cannot be expected to guess at its effects. I am far from saying,
that we are at present by any means fully acquainted with the
powers of the human mind; but we certainly know more of this
instrument than was known four thousand years ago; and therefore,
though not to be called competent judges, we are certainly much
better able than savages to say what is, or is not, within its
grasp. A watch would strike a savage with as much surprise as a
perpetual motion; yet one is to us a most familiar piece of
mechanism, and the other has constantly eluded the efforts of the
most acute intellects. In many instances we are now able to
perceive the causes, which prevent an unlimited improvement in
those inventions, which seemed to promise fairly for it at first.
The original improvers of telescopes would probably think, that
as long as the size of the specula and the length of the tubes
could be increased, the powers and advantages of the instrument
would increase; but experience has since taught us, that the
smallness of the field, the deficiency of light, and the