the nebulous stage, are growing. I have been carried by the
penetrating insight and forcible expression of Dr Tyndall into that
sanctuary of minuteness and of power where molecules obey the laws of
their existence, clash together in fierce collision, or grapple in yet
more fierce embrace, building up in secret the forms of visible
things. I have been guided by Prof. Sylvester towards those serene
heights

"Where never creeps a cloud, or moves a wind,
Nor ever falls the least white star of snow,
Nor ever lowest roll of thunder moans,
Nor sound of human sorrow mounts to mar
Their sacred everlasting calm."

But who will lead me into that still more hidden and dimmer region
where Thought weds Fact, where the mental operation of the
mathematician and the physical action of the molecules are seen in
their true relation? Does not the way to it pass through the very den
of the metaphysician, strewed with the remains of former explorers,
and abhorred by every man of science? It would indeed be a foolhardy
adventure for me to take up the valuable time of the Section by
leading you into those speculations which require, as we know,
thousands of years even to shape themselves intelligibly.

But we are met as cultivators of mathematics and physics. In our
daily work we are led up to questions the same in kind with those of
metaphysics; and we approach them, not trusting to the native
penetrating power of our own minds, but trained by a long-continued
adjustment of our modes of thought to the facts of external nature.