blended
that we distinguish not their outlines. When sea-water evaporates, it
drops crystals freely ; for every grain of salt that goes down, is
itself a gem. A bar of iron is broken, and its whole texture proves to
be an aggregation of crystal particles, showing the angular lines and
cleavage of true crystallization. The granite of the hills is but a
mountain of crystals ; and every pudding-stone, although 'made of
pebbles, has myriads of crystalline grains or fragments of crystals in
and among those pebbles. Finally, the special fact first noted,
develops into a general truth or law, that cohesion in the inorganic
kingdom producing solidification, is actually crystallization ; that we
not merely see nature geo-metrizing, but matter in its profoundest
quality governed by geometrical principles; and therefore that cohesion
in solidification is not a sort of agglutination acting in all
directions alike, which would be well enough for making spheres, but an
axial or polar attraction, bringing out symmetrical forms according to
fixed laws.
Examining
further, more definite laws come out: each species or kind of
substance, wherever found or however made, proves to have its distinct
and constant fundamental crystalline form, so unvarying in angles and
structure, although admitting of modifications by simple ratios, that
it may be as easily known by it, as an animal by its form. These
crystalline forms are cubes, square prisms, rhombic prisms either right
or oblique, etc. ; and in each case, the axes of the prisms, that is,
their relative dimensions, admit of mathematical calculation.
Thus
by widening our field of vision from the single fact to universal
nature, we learn that molecules have their specific forms or
dimensions, and cohesion in solids its mathematical basis. This
fundamental quality of cohesion is sustained by every other
characteristic of crystals: the hardness is different in the direction
of unequal axes; so also the transparency, elasticity,
conduction of heat, and refraction of light; and all in exact
accordance with the law of symmetry in the crystal. Do we not see,
here, that the very molecules, of which the universe is built, were
modelled variously and
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