und us. And yet what strides we have made in the last two
hundred years to improve upon that instrument! With all its wonderful
capabilities, we shall see later on that the eye is a very imperfect
instrument for seeing very small objects, or even large objects when
at a great distance. With the present compound Microscope, only
developed in the last hundred years, and its apochromatic lenses,
invented only in the last forty years, we are able to see and
photograph objects of a minuteness immeasurably beyond the power of
the human eye, and, with our telescopes, we can see and photograph
stars far beyond the possibility of vision by the unaided eye; and
yet, by the stellar spectroscope, we are actually able to examine and
identify the very atoms of which that distant star is composed, or
rather was composed hundreds of thousands of years ago; we can compare
those atoms with the same atoms in our laboratories, and we find that,
though the former are hundreds of thousands of years older than the
latter, they show absolutely no signs of wear or loss of energy,
though they have been for that enormous time, and are still, pulsating
at the rate of not only millions but billions of times per second; and
though the pulsations they emit have travelled across such a vast
depth of space that the mind cannot even imagine the distance, there
has not been any diminution in the numbers of pulsations per second,
nor the slightest slowing down of the rate of flight at which they
started on their journey from that far-off world. If there had been
the _slightest_ change we could detect it at once by means of the
Spectroscope.

With another instrument we are able, not only to hear but to converse
audibly, as long as we like, with another human being a thousand miles
away, who is also sitting comfortably in his own arm-chair and
speaking to us with as much freedom as though we were both in the same
room. With another instrument we can go further, and exchange
thoughts, in a few seconds, with a being on the other side of the
world, by means of a thin wire that is itself fixed, and does not
move, and we have lately invented another means by which we can do the
same, over several thousands of miles, without even a connecting wire.
With another instrument we have gone far beyond the facility with
which the Printing press enabled us to communicate our thoughts to our
fellow human beings, we can actually imprint our very words and
laughter upon a