ngles, and the sides
a little folded inwards. The grains of gray salt which are formed from
sea water affect the figure, or at least the angle, of the cube; and
in the congelations of other salts, and in that of sugar, there are
found other solid angles with perfectly flat faces. Small snowflakes
almost always fall in little stars with 6 points, and sometimes in
hexagons with straight sides. And I have often observed, in water
which is beginning to freeze, a kind of flat and thin foliage of ice,
the middle ray of which throws out branches inclined at an angle of 60
degrees. All these things are worthy of being carefully investigated
to ascertain how and by what artifice nature there operates. But it is
not now my intention to treat fully of this matter. It seems that in
general the regularity which occurs in these productions comes from
the arrangement of the small invisible equal particles of which they
are composed. And, coming to our Iceland Crystal, I say that if there
were a pyramid such as ABCD, composed of small rounded corpuscles, not
spherical but flattened spheroids, such as would be made by the
rotation of the ellipse GH around its lesser diameter EF (of which the
ratio to the greater diameter is very nearly that of 1 to the square
root of 8)--I say that then the solid angle of the point D would be
equal to the obtuse and equilateral angle of this Crystal. I say,
further, that if these corpuscles were lightly stuck together, on
breaking this pyramid it would break along faces parallel to those
that make its point: and by this means, as it is easy to see, it would
produce prisms similar to those of the same crystal as this other
figure represents. The reason is that when broken in this fashion a
whole layer separates easily from its neighbouring layer since each
spheroid has to be detached only from the three spheroids of the next
layer; of which three there is but one which touches it on its
flattened surface, and the other two at the edges. And the reason why
the surfaces separate sharp and polished is that if any spheroid of
the neighbouring surface would come out by attaching itself to the
surface which is being separated, it would be needful for it to detach
itself from six other spheroids which hold it locked, and four of
which press it by these flattened surfaces. Since then not only the
angles of our crystal but also the manner in which it splits agree
precisely with what is observed in the assemblage c