volcanoes: we read occasionally in old chronicles
and modem journals, of showers of red rain.
Our forefathers believed these showers to be
omens of evil days, when the green fields would
be reddened with blood, and the feet of men
shod with red wet; none but the most
ignorant now-a-days regard such showers as
omens of war. The most recent memorandum
which I find among my notes, of rain of this
extraordinary colour, is of a shower which fell
upon the north-western part of the city of Siena,
in Italy, on the 28th of December, 1860. This
shower fell copiously for about two hours, and
the rain was of a reddish colour. No doubt the
natural colour of water, which is colourless in
small quantities, is blue—the hue it displays in
large quantities in the deep sea, when rarefied in
the skies, and when solidified in the glaciers;
but, far from being incredible, it is scarcely
surprising that the heavens should occasionally
discharge red rain. The natural colour of salt
is red. When salt is seen in the rocks of the
salt mines, the reddish hue natural to it is a
surprise to persons who have never seen any
salt in larger quantities than in the grocer's
parcel or perhaps the salt-cellars on the table.
There is a zone only a short way beyond
the mark of low water around our own shores,
which has been called the red shore, because
there the predominant colour is red, where
red star-fishes and strawberry-hued crabs are seen
travelling slowly, or scuttling swiftly in crevices
lined with blood-red skins or films. Small red
crustaceans live in brine. A tiny box-like weed
or algue gives its name to the Red Sea; and a
microscopical fungus sometimes reddens snow.
"Seamen," says Captain Maury, in his book on
The Sea, " tell us of ' red fogs' which they some-
times encounter, especially in the vicinity of the
Cape de Verde Islands." Dr. Clymer reports a
red fog which was encountered in February,
1856, by the United States ship Jamestown. "We
were," he says, "immersed in the dust-fog six
days. The red dust settled thickly on the sails,
rigging, spars, and decks, from which it was
easily collected. It was an impalpable powder
of a brick-dust or cinnamon colour. The
atmosphere was so dusky that we could not have seen
a ship at mid-day beyond a quarter of a mile."
Hundreds of miles from land, this dust is
encountered in quantities which coat the sails of
ships and obscure the sun. Professor Ehrenberg
examined with his microscope, specimens of this
"sea dust" from the Cape de Verde Islands, from
Malta, Genoa, Lyons, and the Tyrol; he was of
opinion that it consisted of the remains of
infusorial organisms from South America, and not
from Africa, and from the south-east trade-wind
region of South America; but that red dust falls
from burning mountains in Africa is positively
proved by the testimony of Captain Playfair,
respecting the shower of dust partially white,
and for several hours resembling red earth,
which fell upon the Abyssinian village of Edd.
The reader of Humboldt's Aspects of Nature
will easily recal to memory his description of the
dust-whirlwinds of the Orinoco, how under the
vertical rays of the scarcely clouded sun the
carbonised turf falls into dust, how the indurated
soil cracks asunder, and how, when opposing
currents of air produce a rotary motion, the sand
rises like conically-shaped clouds in the rarefied
air on the electrically-charged centre of the
whirling current, resembling the waterspout.
The sky sheds a straw-coloured light; the horizon
comes nearer; the steppe contracts; and
with it the heart of the wanderer. The east
wind brings a more and more burning glow,
vegetation shrivels, pools disappear, the crocodile
and the boa bury themselves in the dry
mud, the distant palm-bush seems to hover above
the ground, and the scarcely discernible cattle
and horses roam restless, snuffing the wind.
"The colour of the rain-dust," says Captain
Maury, "when collected into parcels and sent
to Professor Ehrenberg, is ' brick-red' or ' yellow
ochre;' when seen by Humboldt in the air, it
was less deeply shaded, and is described by him
as imparting a straw-colour to the atmosphere.
In the search of spider-lines for the diaphragm
of my telescope, I procured the finest and best
threads from a cocoon of a dirty red colour; but
the threads of this cocoon, as seen singly in the
diaphragm, were of a golden colour; there would
seem no difficulty in reconciling the difference
between the colours of the rain-dust when
viewed in little piles by the microscopist and
when seen attenuated and floating in the wind
by the great traveller." This is ingenious
enough, but the fact that red dust rises from
Jebel Dubbeh, in Africa, shows that it is wrong
to assign it an exclusively South American
origin.

It is not from the rain-dust or red rain alone,
I submit, but from all the strange showers which
come down from the clouds, that we may expect
to obtain a clue to " the circuits of the winds"
even into "the chambers of the south." When
we have numbered the whole of the mountains
which compose the volcanic chain around the
globe, and have ascertained the characteristics of
the dust they emit, it will even then be a hardy
thing for a microscopist to say precisely of such
a parcel of dust, it came from such and such a
volcano or region; for volcanic eruptions are
every now and then issuing from beneath the
depths of the sea. But from a study of all the
things which descend in showers, much must be
learned. Dew, rain, hail, snow, and ice, are, as
everybody knows, all different forms of aqueous
vapour, as differently modified by cold, congealed
into drops, crystallised into flakes, or electrified
into balls. Heat dilates and cold contracts, the
air. The savans compute the temperature of
space at two hundred and thirty-nine degrees
below the zero point of Fahrenheit. There can
be no life there. The spherical form of rain-
drops is an effect of cohesion, but there are
many differences in the constituents of these
drops. M.Pouillet found that the rain-drops from
the vapour of water containing chalk, lime, or any
solid alkali, possess negative electricity; and the
rain-drops from the vapour of water holding in
solution gas, acids, or certain salts, possess