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 crystallize ourselves out of the whole playground. Now, what playground have the minerals! Where are they scattered before they are crystallized; 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 vapor, sometimes nobody knows how, crystallizable 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 crystallizing substance come from?