scale-teeth glitter with some decided hue,
red, green, or blue, while the body of the
scale is clouded with colour and covered with
wavy stripes of wrinkles. In the important
question of scales or no scales, the
micropolariser has the power of extending both
culinary reform and religious liberty. Till
the nineteenth century, the Jews have
believed themselves forbidden by their law to
eat that savoury and nutritious fish, the eel,
on the erroneous assumption that it is scaleless;
because, that the eel has fins (the other
condition of its edibility in Israel), is patent
to the nakedest eye. But, I have now under
my polaro-microscopic eye some beautiful
eel scales,—like elongated oval shields,
burnished with brass, and studded with emeralds,
sapphires, and topazes, grouped in
triangles whose points meet in the centre of
the shield,—which might persuade Jews to
eat and infidels to enjoy. Before quitting
the fishy tribes, be it proclaimed to the
epicurean world, that amongst the prettiest of
polariscope objects are young oysters; not
the little delicious natives which are eaten
in London, but a much smaller sample, with
which your microscopic preparer will supply
you. These are as lovely on the slide as their
elders are dainty on the dish. Everybody
knows that when there is no r in the month,
oysters are out of season, or sick. The milkiness,
which then gives them their distasteful
quality, consists of swarms of oysterlings
which migrate from the maternal bosom and
wander till they acquire some fixed position
in the world. Marvellous to behold, each of
these organised particles of oyster-milk is
furnished with a pair of shells quite as
perfect, though not so big, as those of its
grandmother, and considerably more transparent.

Again, the palates of many gasteropod
mollusks, such as periwinkles, whelks, slugs,
and snails, are highly sensitive to our
extraordinary luminous agent. But, note that
these and numerous other objects for the
polariscope, with the exception of sections,
are best expressly ordered of the preparer,
as such; because many of the parts of an
object, which would only add to its interest
if viewed by ordinary transmitted light, are
better removed when they would only dull
or obscure the details whose special nature
is to exhibit it. This is particularly the
case with the palates of mollusks, which
polarise best the nearer they are brought to
a transparent state. The same circumstance
renders it desirable for the amateur to
possess two preparations of the same organic
object (with crystals the case is different), if
it be interesting without the polariser as well
as with it.

The vegetable world has a less brilliant
display to make, but is still replete with interest.
There are spiral cells and vessels, sections of
wood, proving coal to be of terrestrial origin
and not to have rained from the preadamite
sky, as a philosopher of the day maintains;
fibres, hairs, and scales, and the very curious
minute crystals found in the cells of plants,
called raphides, from the Greek word for
needle, bodkin, or awl. Of these there are
examples in the onion, in rhubarb, in the
American aloe, and others. Cuticles
containing flint are often very beautiful; that of
the common marestail presents a remarkably
neat shawl pattern in stripes. Very curious
optical effects are presented by the various
starches. The starch called tous-les-mois,
having the largest grains, is usually selected
for exhibition.

Crystalline forms, however, are the target
against which polarised light delights to
discharge its most splendid fireworks. Salicine,
a salt extracted from willow trees,
which, it was once hoped, might supersede
quinine in the cure of fever, offers, when
almost an imperceptible film, the appearance
of a pavement consisting not merely of gold,
but of lapis lazuli, ruby, emerald, and opal.
Chlorate of potash strews the field of view
with liberal handfuls of pyramidal jewels.
Chromate of potash, which forms a bright
yellow solution, offers a remarkable choice of
club-shaped crystals, irregularly thrown
together, as if a vast army of theatrical special
constables had thrown their tinselled staves
into a heap, swearing to prevent breaches of
the peace no more. Oxalate of potash, like
several other combinations of oxalic acid, is
a salt of such variety and brilliancy, that its
crystals, floating and glowing in a few drops
of solution on the slide, look as if their form
and colour were the result of a Chinese
imagination in its happiest moments.

The worthies of the last century—and
amongst them the ingenious Henry Baker—
derived great entertainment from watching
the configurations of crystallisation under
the microscope. How some divide and
subdivide after a wonderful order, representing
at the last a winter scene of trees without
leaves: how others perform shootings into the
middle of the drop so as to make a figure not
unlike the framework for the flooring or the
roofing of a house: how distilled verdigrease
assumes an appearance like four leaves of
fern conjoined by their stalks, made them
marvel greatly; for they had no suspicion of
the flashing lights that were latent in the
subjects of their observation. To them, a
rose-shaped group of crystals had beauty
of form only; but, now, if we catch one in
the act of self-formation, we see it spread
like an opening flower whose petals are
striped and blotched with every imaginable
tint.

Still, it is not every saline solution that
readily renders up crystals sensitive to the
impression of the polarised ray. Common
table salt, and alum, although they form
beautiful cubes and pyramids, are apt to
show but the faintest blush of colour; so
savoury and astringent to the palate, they are