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principles of optics better than he does. But he
understands the application of those principles
to astronomical instruments and to
work with them far better than the pure
optical student does. One group may be
in such wise dependent upon several
other groups. Now I do not pretend that
all the ramifications of dependence of one
science upon another can be fully represented
by any scheme of arrangement of the names of those
sciences, even if we limit that the kind of dependence
that we seek to represent to
dependence for principles. But I do
undertake to represent somewhat vaguely
the dependence for principles only of each