can determine only under favourable circumstances. With that
instrument the object may reveal an extended and complicated structure
which it may require a vast labour for the observer fully to explore.

Next in importance to the aid of vision above noted come the
scientific tools which are used in weighing and measuring. These
balances and gauges have attained such precision that intervals so
small as to be quite invisible, and weights as slight as a
ten-thousandth of a grain, can be accurately measured. From these
instruments have come all those precise examinations on which the
accuracy of modern science intimately depends. All these instruments
of precision are the inventions of modern days. The simplest
telescopes were made only about two hundred and fifty years ago, and
the earlier compound microscopes at a yet later date. Accurate
balances and other forms of gauges of space, as well as good means of
dividing time, such as our accurate astronomical clocks and
chronometers, are only about a century old. The instruments have made
science accurate, and have immensely extended its powers in nearly all
the fields of inquiry.

Although the most striking modern discoveries are in the field which
was opened to us by the lens in its manifold applications, it is in
the chemist's laboratory that we find that branch of science, long
cultivated, but rapidly advanced only within the last two centuries,
which has done the most for the needs of man. The ancients guessed
that the substances which make up the visible world were more
complicated in their organization than they appear to our vision. They
even suggested the great truth that matter of all kinds is made up of
inconceivably small indivisible bits which they and we term atoms. It
is likely that in the classic days of Greece men began to make simple