The known is finite, the unknown infinite; intellectually we stand on an islet in the midst of an illimitable ocean of inexplicability. Our business in every generation is to reclaim a little more land, to add something to the extent and the solidity of our possessions.

Mathematics may be compared to a mill of exquisite workmanship, which grinds your stuff to any degree of fineness.

The occurrence of successive forms of life upon our globe is an historical fact, which cannot be disputed; and the relation of these successive forms, as stages of evolution of the same type, is established in various cases.

To a clear eye the smallest fact is a window through which the infinite may be seen.

The secret of genius is to carry the spirit of childhood into maturity.

The man who is all morality and intellect, although he may be good and even great, is, after all, only half a man.

The student of Nature wonders the more and is astonished the less, the more conversant he becomes with her operations; but of all the perennial miracles she offers to his inspection, perhaps the most worthy of admiration is the development of a plant or of an animal from its embryo.