Boundaries which mark off one field of science from another are purely artificial, are set up only for temporary convenience. Let chemists and physicists dig deep enough, and they reach common ground.

A tree nowhere offers a straight line or a regular curve, but who doubts that root, trunk, boughs, and leaves embody geometry?

A calculating engine is one of the most intricate forms of mechanism, a telegraph key one of the simplest. But compare their value.

We despair of changing the habits of men, still we would alter institutions, the habits of millions of men.

Doubt is the beginning, not the end, of wisdom.

Form may be of more account than substance. A lens of ice will focus a solar beam to a blaze.

When a learner, in the fullness of his powers, comes to great truths unstaled by premature familiarity, he rejoices in the lateness of his lessons.