rather, with a certain portion of it. For
we by no means sense all that is sensible, and, as I have already
indicated, our sense impressions are often delusive. The gamut of our
senses is very limited, and also very imperfect both as to extent and
quality. Science is continually bringing new instruments into our
service, some to aid the senses, others to correct them. The
microscope, the microphone, the refracting lens are instances. It used
to be said with great certainty that you cannot see through a brick
wall, but by means of X-rays and a fluorescent screen it is now
possible to do so. I have seen my own heart beating as its image
was thrown on the screen by the Rontgen rays. Many insects,
birds and animals have keener perceptions in some respects than
man. Animalculae and microbic life, themselves microscopic,
have their own order of sense-organs related to a world of life
beyond our ken. These observations serve to emphasise the
great limitation of our senses, and also to enforce the fact that
Nature does not cease to exist where we cease to perceive her.
The recognition of this fact has been so thoroughly appreciated
by thoughtful people as to have opened up the question as to
what these human limitations may mean and to what degree
they may extend.

We know what they mean well enough: the history of human
development is the sequel to natural evolution, and this
development could never have had place apart from the hunger
of the mind and the consequent breaking down of sense limitations by
human invention. As to the extent of our limitations it has been
suggested that just as there are states of matter so fine as to be
beyond the range of vision, so there may be others so coarse as to be
below the sense of touch. We cannot, however, assert anything with
certainty, seeing that proof must always require that a thing must
be brought within our range of perception before we can admit it as
fact. The future has many more wonderful revelations in store for us,
no doubt. But there is really nothing more wonderful than human
faculty which discovers these things in Nature, things that have
always been in existence but until now have been outside our
range of perception. The ultra-solid world may exist.

The relations of our sense-organs to the various degrees of
matter, to solids, fluids, gases, atmosphere and ether, vary in
different individuals to such a wide extent as to create the
greatest diversity of normal fac