d; and often literally with threads;
for the gradually opening rent seems to draw the substance it is filled
with into fibres, which cross from one side of it to the other, and are
partly crystalline; so that, when the crystals become distinct, the
fissure has often exactly the look of a tear, brought together with
strong cross stitches. Now when this is completely done, and all has
been fastened and made firm, perhaps some new change of temperature may
occur, and the rock begin to contract again. Then the old vein must open
wider; or else another open elsewhere. If the old vein widen, it _may_
do so at its centre; but it constantly happens, with well filled veins,
that the cross stitches are too strong to break; the walls of the vein,
instead, are torn away by them; and another little supplementary
vein--often three or four successively--will be thus formed at the side
of the first.

MARY. That is really very much like our work. But what do the mountains
use to sew with?

L. Quartz, whenever they can get it: pure limestones are obliged to be
content with carbonate of lime; but most mixed rocks can find some
quartz for themselves. Here is a piece of black slate from the Buet: it
looks merely like dry dark mud;--you could not think there was any
quartz in it; but, you see, its rents are all stitched together with
beautiful white thread, which is the purest quartz, so close drawn that
you can break it like flint, in the mass; but, where it has been exposed
to the weather, the fine fibrous structure is shown: and, more than
that, you see the threads have been all twisted and pulled aside, this
way and the other, by the warpings and shifting of the sides of the vein
as it widened.

MARY. It is wonderful! But is that going on still? Are the mountains
being torn and sewn together again at this moment?

L. Yes, certainly, my dear: but I think, just as certainly (though
geologists differ on this matter), not with the violence, or on the
scale, of their ancient ruin and renewal. All things seem to be tending
towards a condition of at least temporary rest; and that groaning and
travailing of the creation, as, assuredly, not wholly in pain, is not,
in the full sense, 'until now.'

MARY. I want so much to ask you about that!

SIBYL. Yes; and we all want to ask you about a great many other things
besides.

L. It seems to me that you have got quite as many new ideas as are good
for any of you at present: and I should not lik