it presents itself in such rich luxuriance as in
the mountain brooks about West Point in
the United States, the bottoms of which,
according to Professor Bailey, are literally
covered in the first warm days of spring with
a ferrugineous-coloured mucous matter,
about a quarter of an inch thick, which, on
examination by the microscope, proves to be
filled with millions and millions of these
exquisitely beautiful siliceous bodies. Every
submerged stone, twig, and spear of grass is
enveloped by them; and the vaving plume-like
appearance of a filamentous body covered
in this way is often very elegant.

The microscope startles us with the
incredible information that gigantic mountain
ranges, such as the mighty Andes, are
principally composed of portions of invisible
animalcules. We need take no man's word
for the fact, because we may see with
our own proper eyes, that the remains
of these minute animals have added much
more to the mass of materials which
compose the exterior crust of the globe than
the bones of elephants, hippopotami, and
whales. A stratum of slate in Austria,
fourteen feet thick, was the first that was
discovered to consist almost entirely of minute
flinty shells. This slate, as well as the Tripoli,
found in Africa, is ground to a powder,
and sold for polishing. A microscope shows
you the skeletons in tripoli. Turkey-stone,
used for sharpening razors and knives; and
rotten-stone, of which housemaids are fond
for brightening up their rusty fire-irons; are
also composed of infusorial remains. The
bergh-mehl, or mountain-meal, has been found
in a stratum thirty feet thick in Norway and
Lapland, almost the entire mass being
composed of flinty skeletons of Diatomaceæ. In
times of scarcity, this earth is mixed with flour
by the poor inhabitants both of the north of
Europe and of China to eke out their scanty
subsistence, and cheat their stomachs by the
semblance of a meal. At Holderness, in digging
out a submerged forest on the coast, numbers
of fresh-water fossil Diatomaceæ have been
discovered, though the sea flows over the
place at every tide. Ehrenberg discovered,
in the rock of the volcanic island of Ascension,
many siliceous shells of fresh-water
infusoria; and the same indefatigable investigator
found that the immense ocean of sandy
deserts in Africa were, in great part,
composed of the shells of animalcules.

Very beautiful diatoms are found in the
different kinds of guano—of course when
genuine, and not fabricated out of clay and
gas refuse. It is rather surprising that
the presence or absence of these charming
little curiosities has not been made a test of
the genuineness of the article, especially as
the process of detecting them is not so difficult
or complicated as several of the modes of
analysis usually resorted to by agricultural
chemists. The history of these diatoms is
simply this: they were first swallowed at the
bottom of the Pacific by certain marine
animals, probably shell-fish, sea-mice, star-fish,
and echini. These first devourers have
been devoured by fish proper, and these other
fish by gulls and the rest of the sea-fowl,
whose accumulated excrement forms the
guano. The diatoms are left in the sediment
formed by washing the dung. Abundant
specimens may be obtained from the refuse
which remains when the gardener has poured
off his potfull of liquid manure. The mode of
procuring diatoms from guano, and of
preparing them as microscopic objects, is given
at pages three hundred and thirty-seven and
eight of Dr. Carpenter's learned Microscope
and its Revelations. The marine forms of
these creatures are also found in considerable
numbers in the stomachs of oysters,
scallops, whelks, and other molluscs, especially
the bivalves, or the two-shelled species,
in those of the crab and lobster, and even in
those of the sole, turbot, and other flat fish.
Several species rarely or never occurring in
the usual haunts of their ardent student,
Professor Smith, have been supplied in
abundance by the careful dissection of the above
microphagists. Guano diatoms are mostly
invisible to the naked eye; like Naviculæ, under
a microscope of clearly defining power, they
make you think you are peeping, by mistake,
into some new-invented multiple kaleidoscope.
There are perfectly symmetrical forms, in
circles, some brightly coloured with green
and blue; others spread out in network of
black and white, mixed with fragments of
lace, bright prisms, sharp spikes, and
fragments of patterns for stage finery and
architectural decoration. The complete circlets
are marvels of highly-wrought workmanship,
whose character has been attempted to be
indicated by such names as spider-disc,
sun-shield, sieve-disc, and twist-disc. One
ingenious mode of appropriating these tempting
minutiæ, when found, deserves mention,
here; as the tools for manipulating things
unseen will not obviously occur to every
student. Select a fine hair which has been
split at its free extremity, into from three to
five or six parts; and having fixed it in
common needle-holder, by passing it through
a slit in a piece of cork, use it as a forceps,
with the help of a moderate magnifier.
When the split extremity of the hair touches
the glass slide on which the objects lie, its
parts separate from each other to an amount
proportionate to the pressure; and, on being
brought up to the coveted morsel, are easily
made to seize it, when it can be transferred
as a single specimen to another slide. But
where to find hairs thus split at the extremity?
They may always be had from a
long-used shaving-brush. Those should be
selected which have thin split portions so
closely in contact, that they appear single
until touched at their ends.

And thus the human hand contrives to
meddle with the world unseen, as with