ages,
ancient and modern, were housed within his brain, and, to use the
words of his epitaph, 'he first penetrated the obscurity which had
veiled for ages the hieroglyphics of Egypt.' It fell to the lot of
this man to discover facts in optics which Newton's theory was
incompetent to explain, and his mind roamed in search of a sufficient
theory. He had made himself acquainted with all the phenomena of
wave-motion; with all the phenomena of sound; working successfully in
this domain as an original discoverer. Thus informed and disciplined,
he was prepared to detect any resemblance which might reveal itself
between the phenomena of light and those of wave-motion. Such
resemblances he did detect; and, spurred on by the discovery, he
pursued his speculations and experiments, until he finally succeeded
in placing on an immovable basis the Undulatory Theory of Light.

The founder of this great theory was Thomas Young, a name, perhaps,
unfamiliar to many of you, but which ought to be familiar to you all.
Permit me, therefore, by a kind of geometrical construction which I
once ventured to employ in London, to give you a notion of the
magnitude of this man. Let Newton stand erect in his age, and Young in
his. Draw a straight line from Newton to Young, tangent to the heads
of both. This line would slope downwards from Newton to Young,
because Newton was certainly the taller man of the two. But the slope
would not be steep, for the difference of stature was not excessive.
The line would form what engineers call a gentle gradient from Newton
to Young. Place underneath this line the biggest man born in the
interval between both. It may be doubted whether he would reach the
line; for if he did he would be taller intellectually than Young, and
there was probably none taller. But I do not want you to rest on
English estimates of Young; the German, Helmholtz, a kindred genius,
thus speaks of him: "His was one of the most profound minds that the
world has ever seen; but he had the misfortune to be too much in
advance of his age. He excited the wonder of his contemporaries, who,
however, were unable to follow him to the heights at which his daring
intellect was accustomed to soar. His most important ideas lay,
therefore, buried and forgotten in the folios of the Royal Society,
until a new generation gradually and painfully made the same
discoveries, and proved the exactness of his assertions and the truth
of his demonstrations."

It is