. Then the Leaf-crystals, as I
said, form an immense mass of foliated rocks; and the Granular crystals,
which are of many kinds, form essentially granular, or granitic and
porphyritic rocks; and it is always a point of more interest to me (and
I think will ultimately be to you), to consider the causes which force a
given mineral to take any one of these three general forms, than what
the peculiar geometrical limitations are, belonging to its own
crystals.[150] It is more interesting to me, for instance, to try and
find out why the red oxide of copper, usually crystallising in cubes or
octahedrons, makes itself exquisitely, out of its cubes, into this red
silk in one particular Cornish mine, than what are the absolutely
necessary angles of the octahedron, which is its common form. At all
events, that mathematical part of crystallography is quite beyond girls'
strength; but these questions of the various tempers and manners of
crystals are not only comprehensible by you, but full of the most
curious teaching for you. For in the fulfilment, to the best of their
power, of their adopted form under given circumstances, there are
conditions entirely resembling those of human virtue; and indeed
expressible under no term so proper as that of the Virtue, or Courage of
crystals:--which, if you are not afraid of the crystals making you
ashamed of yourselves, we will try to get some notion of, to-morrow. But
it will be a bye-lecture, and more about yourselves than the minerals,
Don't come unless you like.

MARY. I'm sure the crystals will make us ashamed of ourselves; but we'll
come, for all that.

L. Meantime, look well and quietly over these needle, or thread
crystals, and those on the other two tables, with magnifying glasses,
and see what thoughts will come into your little heads about them. For
the best thoughts are generally those which come without being forced,
one does not know how. And so I hope you will get through your wet day
patiently.

FOOTNOTES:

[150] Note iv.

LECTURE V.

_CRYSTAL VIRTUES._

_A quiet talk, in the afternoon, by the sunniest window of
the Drawing-room. Present_, FLORRIE, ISABEL, MAY, LUCILLA,
KATHLEEN, DORA, MARY, _and some others, who have saved time
for the bye-Lecture._

L. So you have really come, like good girls, to be made ashamed of
yourselves?

DORA (_very meekly_). No, we needn't be made so; we always are.

L. Well, I believe that's truer than most