perimenting_ in such a way
as to get rid of or eliminate the obscuring or disturbing conditions.
Thus, to find out which flower in a garden gives a certain scent, it is
usually enough to rely on observation, going up to the likely flowers
one after the other and smelling them: at close quarters, the greater
relative intensity of the scent is sufficiently decisive. Or we may
resort to a sort of experiment, plucking a likely flower, as to which we
frame the hypothesis (this is the cause), and carrying it to some place
where the air is free from conflicting odours. Should observation or
experiment disprove our first hypothesis we try a second; and so on
until we succeed, or exhaust the known possibilities.

But if the phenomenon is so complex and extensive as a continuous fall
of prices, direct observation or experiment is a useless or impossible
method; and we must then resort to Deduction; that is, to indirect
Induction. If, for example, we take the hypothesis that the fall is due
to a scarcity of gold, we must show that there is a scarcity; what
effect such a scarcity may be expected to have upon prices from the
acknowledged laws of prices, and from the analogy of other cases of an
expanded or restricted currency; that this expectation agrees with the
statistics of recent commerce: and finally, that the alternative
hypothesis that the fall is due to cheaper production is not true;
either because there has not been a sufficient cheapening of general
production; or because, if there has been, the results to be rationally
expected from it are not such as to agree with the statistics of recent
commerce. (Ch. xviii.)

But now suppose that, a phenomenon having been suggested for
explanation, we are unable at the time to think of any cause--to frame
any hypothesis about it; we must then wait for the phenomenon to occur
again, and, once more observing its course and accompaniments and trying
to recall its antecedents, do our best to conceive an hypothesis, and
proceed as before. Thus, in the first great epidemic of influenza, some
doctors traced it to a deluge in China, others to a volcanic eruption
near Java; some thought it a mild form of Asiatic plague, and others
caught a specific microbe. As the disease often recurred, there were
fresh opportunities of framing hypotheses; and the microbe was
identified.

Again, the investigation may take a different form: given a supposed
Cause to find its Effect; e.g., a new chemical e