held together by a force which, if suddenly liberated, would produce a flash of lightning?  Think you that what is carelessly looked upon by the uninitiated as a mere snow-flake, does not suggest higher associations to one who had seen through a microscope the wondrously-varied and elegant forms of snow-crystals?  Think you that the rounded rock marked with parallel scratches, calls up as much poetry in an ignorant mind as in the mind of a geologist, who knows that over this rock a glacier slid a million years ago?  The truth is, that those who have never entered upon scientific pursuits are blind to most of the poetry by which they are surrounded.  Whoever has not in youth collected plants and insects, knows not half the halo of interest which lanes and hedge-rows can assume.  Whoever has not sought for fossils, has little idea of the poetical associations that surround the places where imbedded treasures were found.  Whoever at the sea-side has not had a microscope and aquarium, has yet to learn what the highest pleasures of the sea-side are.  Sad, indeed, is it to see how men occupy themselves with trivialities, and are indifferent to the grandest phenomena—­care not to understand the architecture of the Heavens, but are deeply interested in some contemptible controversy about the intrigues of Mary Queen of Scots!—­are learnedly critical over a Greek ode, and pass by without a glance that grand epic written by the finger of God upon the strata of the Earth!

We find, then, that even for this remaining division of human activities, scientific culture is the proper preparation.  We find that aesthetics in general are necessarily based upon scientific principles; and can be pursued with complete success only through an acquaintance with these principles.  We find that for the criticism and due appreciation of works of art, a knowledge of the constitution of things, or in other words, a knowledge of science, is requisite.  And we not only find that science is the handmaid to all forms of art and poetry, but that, rightly regarded, science is itself poetic.

* * * * *

Thus far our question has been, the worth of knowledge of this or that kind for purposes of guidance.  We have now to judge the relative value of different kinds of knowledge for purposes of discipline.  This division of our subject we are obliged to treat with comparative brevity; and happily, no very lengthened treatment of it is needed.  Having found what is best for the one end, we have by implication found what is best for the other.  We may be quite sure that the acquirement of those classes of facts which are most useful for regulating conduct, involves a mental exercise best fitted for strengthening the faculties.  It would be utterly contrary to the beautiful economy of Nature, if one kind of culture were needed for the gaining of information and another kind were needed as a mental gymnastic.  Everywhere throughout creation