ions which cannot be
ignored, because they spring from the very nature of reason, and
which cannot be answered, because they transcend the powers of human
reason." (Tr.)

[111] In the rare _Notes_ that he has left, James Watt writes that
one afternoon he had gone out for a stroll on the Green at Glasgow,
and his thoughts were absorbed with the experiments in which he was
busied, trying to prevent the cooling of the cylinder. The thought
then came to him that steam, being an elastic fluid, should expand
and be precipitated in a space formerly void; and having made a
vacuum in a separate vessel and opened communication between the
steam of the cylinder and the vacant space, we see what should
follow. Thus, having imagined the masterpiece of his discovery, he
enumerates the processes that, employed in turn, allowed him to
perfect it.

[112] For further information we refer to the _Logique de
l'hypothese_, by E. Naville, from which are borrowed most of the
facts here given.

[113] This much-criticised defect has been only partially overcome
in our methods of education through "object" lessons, and, if we may
call them so, evolutionary methods, showing to the child "wie es
eigentlich gewesen." Cf. J. Dewey, "_The School and Society_." (Tr.)

[114] See above, Part Two, chapter IV.

[115] Preface to the _Critique of Pure Reason_.

[116] Colozza, _L'immaginazione nella Scienza_ (Paravia, 1900), pp.
89 ff. In this author will be found abundant details respecting
famous discoveries or experiments--those of Galileo, Franklin,
Grimaldi, etc.

[117] Here is an example in confirmation, taken from Duclaux's book
on Pasteur: Herschel established a relation between the crystalline
structure of quartz and the rotatory power of the substance; later
on, Biot established it for sugar, tartaric acid, etc.--i.e., for
substances in solution, whence he concluded that the rotatory power
is due to the form of the molecule itself, not to the arrangement of
the molecules in relation to one another. Pasteur discovered a
relation between molecular dyssymmetry and hemiedry, and the study
of hemiedry in crystals led him logically to that of fermentation
and spontaneous generation.

[118] On this point cf. Fouillee, _L'Avenir de la Metaphysique_, pp.
79 ff.

CHAPTER V

THE PRACTICAL AND MECHANICAL IMAGINATION

The study of the practical imagination is not without difficulties.
First of all, it has not hitherto attracted psycholo