take in the impressions thus generated, the human eye and brain,
however we may simplify our conceptions of their action,[8] must be
highly complex.

Whence this triple complexity? If what are called material purposes
were the only end to be served, a much simpler mechanism would be
sufficient. But, instead of simplicity, we have prodigality of
relation and adaptation--and this, apparently, for the sole purpose of
enabling us to see things robed in the splendours of colour. Would it
not seem that Nature harboured the intention of educating us for other
enjoyments than those derivable from meat and drink? At all events,
whatever Nature meant--and it would be mere presumption to dogmatize
as to what she meant--we find ourselves here, as the upshot of her
operations, endowed, not only with capacities to enjoy the materially
useful, but endowed with others of indefinite scope and application,
which deal alone with the beautiful and the true.




LECTURE II.

ORIGIN OF PHYSICAL THEORIES
SCOPE OF THE IMAGINATION
NEWTON AND THE EMISSION THEORY
VERIFICATION OF PHYSICAL THEORIES
THE LUMINIFEROUS ETHER
WAVE THEORY OF LIGHT
THOMAS YOUNG
FRESNEL AND ARAGO