make the new inquiry--which, should it cast no immediate light on the
answer sought, can yet hardly fail to be a step towards final discovery.
Every experiment has its origin in hypothesis; without the scaffolding
of hypothesis, the house of science could never arise. And the
construction of any hypothesis whatever is the work of the imagination.
The man who cannot invent will never discover. The imagination often
gets a glimpse of the law itself long before it is or can be
_ascertained_ to be a law. [Footnote: This paper was already written
when, happening to mention the present subject to a mathematical friend,
a lecturer at one of the universities, he gave us a corroborative
instance. He had lately _guessed_ that a certain algebraic process could
be shortened exceedingly if the method which his imagination suggested
should prove to be a true one--that is, an algebraic law. He put it to
the test of experiment--committed the verification, that is, into the
hands of his intellect--and found the method true. It has since been
accepted by the Royal Society.

Noteworthy illustration we have lately found in the record of the
experiences of an Edinburgh detective, an Irishman of the name of
McLevy. That the service of the imagination in the solution of the
problems peculiar to his calling is well known to him, we could adduce
many proofs. He recognizes its function in the construction of the
theory which shall unite this and that hint into an organic whole, and
he expressly sets forth the need of a theory before facts can be
serviceable:--

"I would wait for my 'idea'.... I never did any good without mine....
Chance never smiled on me unless I poked her some way; so that my
'notion,' after all, has been in the getting of it my own work only
perfected by a higher hand."