most important in all that relates to our understanding of Nature, is
sight, or the capacity which enables us to appreciate the movement of
those very small waves of ether which constitute light. The eminent
peculiarity of sight is that it may give us information concerning
things which are inconceivably far away; it enables us to discern the
light of suns probably millions of times as remote from us as is the
centre of our own solar system.

Although much of the pleasure which the world affords us comes through
the other senses, the basis of almost all our accurate knowledge is
reported by sight. It is true that what we have observed with our eyes
may be set forth in words, and thus find its way to the understanding
through the ears; also that in many instances the sense of touch
conveys information which extends our perceptions in many important
ways; but science rests practically on sight, and on the insight that
comes from the training of the mind which the eyes make possible.

The early inquirers had no resources except those their bodies
afforded; but man is a tool-making creature, and in very early days he
began to invent instruments which helped him in inquiry. The earliest
deliberate study was of the stars. Science began with astronomy, and
the first instruments which men contrived for the purpose of
investigation were astronomical. In the beginning of this search the
stars were studied in order to measure the length of the year, and
also for the reason that they were supposed in some way to control the
fate of men. So far as we know, the first pieces of apparatus for this
purpose were invented in Egypt, perhaps about four thousand years
before the Christian era. These instruments were of a simple nature,
for the magnifying glass was not yet contrived, and so the telescope
was impossible. They consisted of arrangements of straight edges and