without impropriety, be included among methods of direct
observation and experiment.

These, then, with such assistance as can be obtained from
deduction, compose the available resources of the human mind for
ascertaining the laws of the succession of phenomena. Before
proceeding to point out certain circumstances by which the
employment of these methods is subjected to an immense increase
of complication and of difficulty, it is expedient to illustrate the
use of the methods by suitable examples drawn from actual
physical investigations. These, accordingly, will form the subject
of the succeeding chapter.

Dr. Whewell has expressed a very unfavorable opinion of the
utility of the four methods, as well as of the aptness of the examples
by which I have attempted to illustrate them. His words are
these: ¹

Upon these methods, the obvious thing to remark is, that they
take for granted the very thing which is most difficult to discover,
the reduction of the phenomena to formulae such as are here
presented to us. When we have any set of complex facts offered
to us; for instance, those which were offered in the cases of dis-
covery which I have mentioned -- the facts of the planetary paths,
of falling bodies, of refracted rays, of cosmical motions, of chemical
analysis; and when, in any of these cases, we would discover the
law of nature which governs them, or, if anyone chooses so to term
it, the feature in which all the cases agree, where are we to look

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