lops that form, and no
other. But the force which crystallises a mineral appears to be chiefly
external, and it does not produce an entirely determinate and individual
form, limited in size, but only an aggregation, in which some limiting
laws must be observed.

MARY. But I do not see much difference, that way, between a crystal and
a tree.

L. Add, then, that the mode of the energy in a living thing implies a
continual change in its elements; and a period for its end. So you may
define life by its attached negative, death; and still more by its
attached positive, birth. But I won't be plagued any more about this,
just now; if you choose to think the crystals alive, do, and welcome.
Rocks have always been called 'living' in their native place.

MARY. There's one question more; then I've done.

L. Only one?

MARY. Only one.

L. But if it is answered, won't it turn into two?

MARY. No; I think it will remain single, and be comfortable.

L. Let me hear it.

MARY. You know, we are to crystallise ourselves out of the whole
playground. Now, what playground have the minerals? Where are they
scattered before they are crystallised; and where are the crystals
generally made?

L. That sounds to me more like three questions than one, Mary. If it is
only one, it is a wide one.

MARY. I did not say anything about the width of it.

L. Well, I must keep it within the best compass I can. When rocks either
dry from a moist state, or cool from a heated state, they necessarily
alter in bulk; and cracks, or open spaces, form in them in all
directions. These cracks must be filled up with solid matter, or the
rock would eventually become a ruinous heap. So, sometimes by water,
sometimes by vapour, sometimes nobody knows how, crystallisable matter
is brought from somewhere, and fastens itself in these open spaces, so
as to bind the rock together again, with crystal cement. A vast quantity
of hollows are formed in lavas by bubbles of gas, just as the holes are
left in bread well baked. In process of time these cavities are
generally filled with various crystals.

MARY. But where does the crystallising substance come from?

L. Sometimes out of the rock itself; sometimes from below or above,
through the veins. The entire substance of the contracting rock may be
filled with liquid, pressed into it so as to fill every pore;--or with
mineral vapour;--or it may be so charged at one place, and empty at
another. There's no end to the