erved before, and
which he knew were not produced either by potash or soda. He then set
to work to analyse the mixture, and ultimately succeeded in separating
two new alkaline substances. When he had succeeded in getting them
separate, it was of course by the Method of Difference that he
ascertained them to be capable of producing the lines that had excited
his curiosity.

[Footnote 1: Bain's _Logic_, vol. ii. p. 64.]

[Footnote 2: Herschel's _Discourse_, Sec. 158.]

[Footnote 3: De Morgan's _Budget of Paradoxes_, p. 237.]

CHAPTER VII.

THE METHOD OF EXPLANATION.

Given perplexity as to the cause of any phenomenon, what is our
natural first step? We may describe it as searching for a clue: we
look carefully at the circumstances with a view to finding some
means of assimilating what perplexes us to what is already within our
knowledge. Our next step is to make a guess, or conjecture, or, in
scientific language, a hypothesis. We exercise our Reason or _Nous_,
or Imagination, or whatever we choose to call the faculty, and try to
conceive some cause that strikes us as sufficient to account for the
phenomenon. If it is not at once manifest that this cause has really
operated, our third step is to consider what appearances ought to
present themselves if it did operate. We then return to the facts in
question, and observe whether those appearances do present themselves.
If they do, and if there is no other way of accounting for the effect
in all its circumstances, we conclude that our guess is correct,
that our hypothesis is proved, that we have reached a satisfactory
explanation.

These four steps or stages may be distinguished in most protracted
inquiries into cause. They correspond to the four stages of what
Mr. Jevons calls the Inductive Method _par excellence_, Preliminary
Observation, Hypothesis, Deduction and Verification. Seeing that the
word Induction is already an overloaded drudge, perhaps it would be
better to call these four stages the Method of Explanation. The word
Induction, if we keep near its original and most established meaning,
would apply strictly only to the fourth stage, the Verification, the
bringing in of the facts to confirm our hypothesis. We might call the
method the Newtonian method, for all four stages are marked in the
prolonged process by which he made good his theory of Gravitation.

To give the name of Inductive Method simply to all the four stages
of an orderly