clearly reveals the
reverse process of construction. In this fashion, and in strict
accordance with this hexangular type, every ice molecule takes its
place upon our ponds and lakes during the frosts of winter. To use
the language of an American poet, 'the atoms march in tune,' moving to
the music of law, which thus renders the commonest substance in nature
a miracle of beauty.

It is the function of science, not as some think to divest this
universe of its wonder and mystery, but, as in the case before us, to
point out the wonder and the mystery of common things. Those
fern-like forms, which on a frosty morning overspread your
windowpanes, illustrate the action of the same force. Breathe upon
such a pane before the fires are lighted, and reduce the solid
crystalline film to the liquid condition; then watch its subsequent
resolidification. You will see it all the better if you look at it
through a common magnifying glass. After you have ceased breathing,
the film, abandoned to the action of its own forces, appears for a
moment to be alive. Lines of motion run through it; molecule closes
with molecule, until finally the whole film passes from the state of
liquidity, through this state of motion, to its final crystalline
repose.

I can show you something similar. Over a piece of perfectly clean
glass I pour a little water in which certain crystals have been
dissolved. A film of the solution clings to the glass. By means of a
microscope and a lamp, an image of the plate of glass is thrown upon
the screen. The beam of the lamp, besides illuminating the glass,
also heats it; evaporation sets in, and at a certain moment, when the
solution has become supersaturated, splendid branches of crystal shoot
out over the screen. A dozen square feet of surface are now covered
by those beautiful forms. With another solution we obtain crystalline
spears, feathered right and left by other spears. From distant nuclei
in the middle of the field of view the spears shoot with magical
rapidity in all directions. The film of water on a window-pane on a
frosty morning exhibits effects quite as wonderful as these. Latent
in these formless solutions, latent in every drop of water, lies this
marvellous structural power, which only requires the withdrawal of
opposing forces to bring it into action.

The clear liquid now held up before you is a solution of nitrate of
silver--a compound of silver and nitric acid. When an electric