fter
years of careful study of nature, he published in 1859 _The Origin of
Species by Natural Selection_, an epoch-making work, which had a
far-reaching effect on the thought of the age.

The influence of his doctrine of evolution is especially apparent in
Tennyson's poetry, in George Eliot's fiction, in religious thought,
and in the change in viewing social problems. In his _Synthetic
Philosophy_, Herbert Spencer (1820-1903), philosopher and
metaphysician, applied the doctrine of evolution not only to plants
and animals but also to society, morality, and religion.

Two eminent scientists, John Tyndall (1820-1893) and Thomas Huxley
(1825-1895), did much to popularize science and to cause the age to
seek a broader education. Tyndall's _Fragments of Science_ (1871)
contains a fine lecture on the _Scientific Use of the Imagination_, in
which he becomes almost poetic in his imaginative conception of
evolution:--

"Not alone the more ignoble forms of animalcular
or animal life, not alone the nobler
forms of the horse and lion, not alone the exquisite
and wonderful mechanism of the human
body, but the human mind itself,--emotion,
intellect, will, and all their phenomena,--were
once latent in a fiery cloud... All our philosophy, all our poetry,
all our science, and all our art,--Plato, Shakespeare, Newton, and
Raphael,--are potential in the fires of the sun."

[Illustration: JOHN TYNDALL.]

Unlike Keats in his _Lamia_, Tyndall is firm in his belief that
science will not clip the wings of imagination. In the same lecture he
says:--

"How are we to lay hold of the physical basis of light, since, like
that of life itself, it lies entirely without the domain of the
senses? We are gifted with the power of imagination and by this
power we can lighten the darkness which surrounds the world of the
senses... Bounded and conditioned by cooeperant reason, imagination
becomes the mightiest instrument of the physical discoverer.
Newton's passage from a falling apple to a falling moon was at the
outset a leap of the imagination."

Huxley was even a more brilliant interpreter of science to popular
audiences. His so-called _Lay Sermons_ (1870) are invigorating
presentations of scientific and educational subjects. He awakened many
to a sense of the importance of "knowing the laws of the physical
world" and "the relations of cause and effect therein." Nowhere is he
more impressive than where he forc