LUMINOUS SHOWERS.
In many old works, accounts are found of so-called showers of fire,
during which the entire heavens seemed filled with gleaming drops, that
threatened to burn every living thing, but were in reality harmless;
the exhibition being merely another instance of this strange phenomenon
of heatless light.
Some years ago a party of peasants were making the ascent of one of
the high peaks of the Alps, when they were caught in a rain-storm,
which produced a demoralizing effect upon them. As the rain fell, it
seemed to become luminous, and drops of fire apparently ran from their
clothing and beards. Their attempts at brushing it away, while adding
to the startling nature of the phenomenon, showed, however, that it was
perfectly harmless.
Dr. Phipson records some interesting instances of this kind of
phosphorescence, of which the following may be cited:--
M. de Thielan observed on Jan. 25, 1822, near Freyburg, a most
extraordinary spectacle. A heavy snow had been falling during the
early part of the evening, and the trees, branches, limbs, and leaves
quivered and scintillated with a resplendent bluish light, while the
drops of rain upon the grass left golden trains as they dripped to the
ground.
[Illustration:
PLATE XXIII.
DEEP SEA ANGLER.
(_Melanocetus johnstoni, Gth._)]
Arrago records similar occurrences: In 1731 a priest named Hallai, who
lived at Lessay, near Constance, states that he observed one evening
during a severe thunder-storm, rain falling which looked like _drops
of red-hot liquid metal_.
Bergman, the eminent Swedish chemist, communicated to the Royal Society
of London, in 1761, that late in the afternoon upon two occasions,
though hearing no thunder, he had seen rain which glittered as it fell
upon the ground, making it look as if covered with waves of fire.
M. Pasumot, on May 3, 1768, was overtaken, while walking near
Arnay-le-Duc, on an open plain, by a very heavy storm. The rain
collecting on the brim of his hat, he stooped his head to allow it to
run off, when to his astonishment, as it encountered that which fell
from the clouds, at about twenty inches from the ground, _sparks were
emitted_ between the two portions of liquid.
During January, 1822, Lampadius was told by the miners of Freyburg,
that they had observed during a storm, _sleet_ which _emitted light_
when it fell upon the ground.
A friend of Howard, the meteorologist, stated to him, that while going
from London to Bow on the 19th of May, 1809, there came up a very
severe storm; and he observed the rain emit light as it struck the
earth.
On the 28th of October, 1772, the Abbé Bertholon, who was travelling
to Lyons from Brignai, early in the morning was overtaken by a violent
storm of rain and hail. The _rain and hail-stones emitted light_ as
they fell upon the metallic mounting of his horse’s trappings.
Luminous hail has often been observed; and when we remember that
hail-stones sometimes attain great size, we can imagine the scene
occasioned by a fall where each stone is phosphorescent. Ordinary
hail-stones are the size of small peas, but they occasionally occur
large enough to kill human beings; and I have seen them so large in the
Sierra Madre Mountains that any shelter was preferable to exposure to
them. In 1707 a hail-storm occurred at the town of Como, Switzerland,
doing an incredible amount of damage, some of the stones weighing
nearly ten ounces. Darwin describes a storm upon the South American
pampas, in which the stones that fell were large enough to kill
powerful animals.
Ice has often been observed to emit luminous sparks; and probably one
of the grandest spectacles ever witnessed, is the luminous cap of a
snow-covered mountain. The glaciers of the Alps have been seen bathed
in a soft phosphoric glow, the icy rivers being distinctly marked by
the phenomenon, which is so brilliant, at times, that the appearance
of a second sunset is occasioned. Not only are the summits of Alpine
peaks and the glaciers luminous, but the valleys of Piedmont, Valais,
and others have been seen to emit from their covering of snow a soft
blue light of singular beauty. So intense is this light about the cap
of Mount Blanc, it has been photographed. Luminous vapors or mists
may be mentioned in this connection. Several times in the history of
this country, luminous mists or fogs have been recorded. Massachusetts
was visited by one some years ago, in which the fog was so dense that
observers a few feet away were invisible, yet darkness was not an
accompaniment; the mist seemed to be light-emitting itself, having a
reddish, metallic hue. Others described it as a fiery red or yellow,
while to some it appeared to be composed of faintly luminous matter.
In the year 1783 all Europe and a portion of Asia were enveloped in a
dense fog of a most remarkable nature. It was termed “dry,” as even at
night no dampness was observed. It was first seen at Copenhagen, its
coming being heralded by severe storms. A few weeks later it appeared
in various parts of France, and rapidly seemed to spread over Europe
and portions of Asia. During the day it had a metallic glow, which at
night changed to a phosphorescent light, so brilliant that ordinary
print could be read by it. Many attempts to explain it were made by the
savants of the day, and it was universally supposed to be due to the
earthquakes and volcanic eruptions which were of unusual severity that
year.
A somewhat similar fog appeared in the United States, a portion of
Europe, and Africa in August, 1831. The daylight was perceptibly
diminished, while at night a conspicuous phosphorescent light was
emitted. A remarkable luminous fog occurred in Switzerland in 1859. M.
L. F. Wartmann of Geneva states that the strange light was observed on
five successive nights, and apparently proceeded from a heavy dry fog
that hung over Geneva during the time. The light was so brilliant that
this gentleman distinguished the smallest objects upon his table with
perfect ease, no other light being in the apartment. The light caused
general comment in the places in which it appeared, and a traveller
between Geneva and Annemassi stated that he readily found the road by
its means. Dr. Verdeil of Lausanne describes a fog which diffused so
much light that distant objects were perfectly visible at night.
Among the phenomena which attended the eruption of Vesuvius in 1794 was
one which did not tend to allay the fears of the people. During the day
a fine dust filled the air about Naples, which was not particularly
noticeable; but as night came on, it emitted a pale though distinct
phosphorescent light. An English gentleman sailing near Torre del Greco
noticed that where the dust collected upon his hat it was luminous, and
no little consternation was caused among the superstitious sailors by
the occurrence.
Luminous dust-showers have been noticed in several localities; and the
peculiar glows that were seen in this country a few years ago were
accredited by many to them, the supposition being that dust, perhaps
from volcanic eruptions, was floating about in the upper strata of the
atmosphere. Many other explanations were given, and the literature upon
the subject is extremely voluminous and interesting.
The amount of material floating about in the upper regions of the air
is perhaps little realized by my young readers, and some reference to
the phenomenon may be of interest.
Professor Nordenskjöld has for many years been a close observer of
dust of all kinds that has fallen upon the earth in rain or snow; and
it was his good fortune, during the expedition of the “Vega,” to prove
beyond a doubt the presence of cosmic dust. For many years we have
been assured by astronomers that the earth was being bombarded, as it
were, continually, by innumerable meteors. The moment they enter our
domain, we observe the spectacle of their ignition. In a moment they
are reduced to ashes, and the fine impalpable dust drops slowly, an
invisible shower, upon the earth. When such showers are intensified, it
is not impossible that some outward and visible phenomena may be the
result.
In the search for this cosmic dust, the far North, where the surface
is covered by an almost continuous coating of snow and ice, offers
a wide and promising field for investigation. Here no other dust
prevails. Professor Nordenskjöld first found cosmic dust in the North
at Spitzbergen. The second discovery, off the Taimar coast, seemed to
be in the form of yellow specks lying on the snow. They were at first
supposed to be diatomaceous ooze;[49] but when placed in the hands
of Dr. Kjellman, he pronounced them to be pale yellow crystals, and,
curious enough, formed of carbonate of lime. “The original composition
and origin of this substance,” says Professor Nordenskjöld, “appears
to me exceedingly enigmatical. It was not carbonate of lime, for the
crystals were rhomboidal, and did not show the cleavage of calcite.
Nor can there be a question of its being arragonite, because this
mineral might indeed fall asunder of itself; but in that case the newly
formed powder ought to be crystalline. Have the crystals originally
been a new hydrated carbonate of lime formed by crystallizing out at
a temperature of ten or twenty degrees above the freezing point? In
such case they ought not to have been found on the surface of the
_snow_, but lower, on the surface of the _ice_. Or have they fallen
down from the inter-planetary spaces to the surface of the earth, and
before crumbling down have had a composition differing from terrestrial
substances, in the same way as various chemical compounds found in
recent times in meteoric stones? The occurrence of the crystals in
the uppermost layer of snow, and their falling asunder in the air,
tell in favor of this view. Unfortunately there is no possibility of
settling these questions; but at all events this discovery is a further
incitement to those who travel in the high North, to collect with
extreme care, from snow-fields lying far from the ordinary routes of
communication, all foreign substances, though apparently of trifling
importance.”
The investigations of the Swedish naturalist in this field are of
exceeding interest. His first attempt to obtain meteoric dust was at
Stockholm, where, in December, 1871, there was a great fall of snow,
the heaviest ever known. On the last days of the storm, after the
atmosphere had been presumably purified of extraneous substances, he
collected a cubic metre of snow, melted it over a fire, and found that
after the water had evaporated a residue of black powder remained,
in which were many grains of metallic iron, that were attracted by a
magnet. In 1872 his brother made a similar examination of the snow, in
a quiet locality near the remote village of Evois, Finland. The snow
upon being melted also gave the same black powder and metallic iron.
The investigations of Nordenskjöld himself, conducted in Spitzbergen,
as previously mentioned, were the most satisfactory. The observations
were made in 80° north latitude, and 13° to 150° east longitude, in
the layer of snow that covered the ice. An imaginary section was as
follows: (1), new fallen snow; (2), a layer of hardened old snow,
eight millimetres in thickness; (3), a layer of snow, conglomerated to
a crystalline granular mass; and (4), common granular hardened snow.
Layer three was full of small black grains, among which were found
numerous metallic particles, that were attracted by the magnet, and
found to contain iron, cobalt, and possibly nickel also.
In his visit to Greenland in 1870, Nordenskjöld found in the dust
that lay on the inland ice, grains of metallic iron and cobalt. “The
main mass,” he says, “consisted of a crystalline, double refracting
silicate, drenched through with an ill-smelling organic substance.
The dust was found in large quantities at the bottom of innumerable
small holes in the surface of the inland ice. This dust could scarcely
be of volcanic origin, because by its crystalline structure it
differs completely from the glass dust that is commonly thrown out of
volcanoes, and is often carried by the wind to very remote regions;
as also from the dust which, in March, 1875, fell at many places in
the middle of Scandinavia, and which was proved to have been thrown
out by volcanoes in Iceland.” Professor Nordenskjöld’s estimate of the
quantity of dust shows that it has been in past ages a not unimportant
factor, perhaps, in its addition to the crust. He says, “I estimate the
quantity of the dust that was found on the ice north of Spitzbergen, at
from .01 to 1 milligram per square metre; and probably the whole fall
of dust for the year far exceeded the latter figure. But a milligram on
every square metre of the surface of the earth amounts for the globe
to five hundred million kilograms (say half a million tons). Such a
mass, collected year by year during the geological ages, of a duration
probably incomprehensible by us, becomes a consideration too important
to be neglected, when the fundamental facts of the geological history
of our planet are enumerated. A continuation of these investigations
will perhaps show that our globe has increased gradually from a small
beginning to the dimensions it now possesses; that a considerable
quantity of the constituents of our sedimentary strata, especially of
those that have been deposited in the open sea far from land, are of
cosmic origin; and will throw an unexpected light on the origin of the
fire-hearths of the volcanoes, and afford a simple explanation of the
remarkable resemblance which unmistakably exists between plutonic rocks
and meteoric stones.”
Such enormous masses of material could well explain the rosy and other
curious lights that are from time to time observed. But cosmic dust
is not the only matter in the air that could occasion the phenomena;
the atmosphere is constantly filled with innumerable forms caught up
by currents and carried to inconceivable heights, and thus to great
distances, to be precipitated to the earth in hail, snow, or rain.
Near St. Domingo, Darwin tells us, the atmosphere became thick and
hazy from the impalpable fine dust that actually injured their
astronomical instruments. “The morning before we anchored at Porto
Praya,” he says, “I collected a little packet of this brown-colored
dust, which appeared to have been filtered from the wind by the gauze
of the vane at the masthead. Mr. Lyell has also given me four packets
of dust which fell on a vessel a few hundred miles northward of these
islands. Professor Ehrenberg finds that this dust consists in great
part of _infusoria_ with siliceous shields, and of the siliceous
tissue of plants. In five little packets which I sent him, he has
ascertained no less than sixty-seven different organic forms. The
_infusoria_, with the exception of two marine species, are all
inhabitants of fresh water. I have found no less than fifteen different
accounts of dust having fallen on vessels when far out in the Atlantic.
From the direction of the wind whenever it has fallen, and from its
having always fallen during those months when the harmattan is known to
raise clouds of dust high into the atmosphere, we may feel sure that
it all comes from Africa. It is, however, a very singular fact, that,
although Professor Ehrenberg knows many species of _infusoria_
peculiar to Africa, he finds none of them in the dust which I sent him;
on the other hand, he finds in it two species which hitherto he knows
as living only in South America. The dust falls in such quantities
as to dirty every thing on board, and to hurt people’s eyes; vessels
even have run ashore, owing to the obscurity of the atmosphere. It has
often fallen on ships when more than a thousand miles from the coast
of Africa, and at points sixteen hundred miles distant in a north and
south direction. In some dust which was collected on a vessel three
hundred miles from the land, I found particles of stone, above the
thousandth of an inch square, mixed with finer matter. After this fact,
one need not be surprised at the diffusion of the far lighter and
smaller sporules of cryptogamic plants.”
The extent to which dust and ashes can be taken up and held by air
currents is shown in volcanoes. In 1810 the ashes from a volcano at
St. Vincent were wafted to Barbados, nearly a hundred miles; and in
1835 the material thrown from a volcano in Guatemala to Jamaica, eight
hundred miles. As intimated, these showers are not all inorganic, but
are often living or fossil animals or plants that are floating about.
Such are the reddish or gray showers that are frequently met with off
the African coast, and when in the snow they are called “blood-rains.”
The one in 1755, near Lago Maggiore, covered over two hundred square
leagues, causing a panic among the inhabitants. For a distance of nine
feet below the surface, the snow was blood red, the atmosphere appeared
red and fiery, while at sunrise and sunset a rosy hue pervaded every
thing. When this shower fell and there was no snow, the earthy deposit
accumulated an inch deep; and it has been estimated that, supposing it
to average two lines in depth, there would be for each square mile an
amount equal to nearly three thousand cubic feet. A similar panic was
caused some years ago by a swarm of butterflies. Everywhere they left
a drop of blood-colored fluid, so that the fences, houses, and cattle
were covered with it. The insects were so numerous that they obstructed
the vision.
In the “blood-rains” of Italy, and generally in such instances, the
red hue comes from red oxide of iron. At a single shower in Lyons in
1846, Ehrenberg estimated that seven hundred and twenty thousand pounds
of material fell, ninety thousand pounds of which were microscopic
organisms, including thirty-nine species of siliceous diatoms, and many
others of great beauty of form and shape.
Ehrenberg enumerates a very large number of these showers, referring
to Homer’s “Iliad” for one of the earliest known; and asks, with such
facts before us, how many thousand millions of hundred-weight of
microscopic organism have reached the earth since Homer’s time? The
whole number of species made out is over three hundred. The species, as
far as ascertained, are not African; fifteen are North American. But
the origin of the dust is yet unknown. The zone in which these showers
occur covers Southern Europe and Northern Africa, with the adjoining
portion of the Atlantic, and the corresponding latitudes in Western and
middle Asia.
When blown along by the wind, these showers perform another office
besides affecting, perhaps, the color or tint of the atmosphere; they
wear away rock, and polish and furrow it. Such work can be seen in the
granite rocks at the San Bernardino Pass in California. Quartz is
polished, and hard gems left weathered out; while at Cape Cod ordinary
sand has been known to wear holes through glass windows by continually
blowing against them.
[Illustration:
PLATE XXIV.
PELICAN FISH.
(_Eyrypharyx pelecanoides._)]
An ingenious instrument has been invented to capture these flying
objects of the air. It is called by the inventor, Doctor Miguel, the
æroscope, and is really a net for animals invisible to the naked eye.
Many objects are phosphorescent when struck, or when divided into
thin laminæ. Some simple materials for such experiments are chlorate
of potash, fluor-spar, feld-spar, sugar, etc. By placing any of
these in a mortar, and grinding them in the dark, flashes of light
will be seen, powdered sugar often making a striking display. A
beautiful and effective exhibition can be produced by placing a small
amount of phosphuret of calcium in water; decomposition follows, and
phosphuretted gas is evolved. As the bubbles of gas rise and come in
contact with the atmosphere, they seem to take fire. If in a dark room,
luminous rings are seen rising, and they can be made to take various
shapes by using a fan. A trick often performed by magicians is to hand
around a marble, and then pretend to render it luminous by blowing upon
it. This trick consists in having small balls at hand, of a material
that can readily be rendered luminous by the application of heat. These
substances can be easily made.
A fine light is produced by taking,--
Barium sulphate (C P.) 32 parts
Magnesium carbonate (C P.) 1 part
Sulphur (C P.) 1 part
Gum tragacanth q. s.
This should be made into balls of a convenient size, dried at a
moderate temperature, and kept in a crucible at a red heat for about an
hour. Allow them to cool slowly, and then place in a glass-stoppered
bottle before their heat has disappeared. When required for use, expose
them to the sun or any strong light, and they will become luminous, and
continue so for many hours.
Another formula is:--
Strontium sulphate (C P.) 22 parts
Sulphur (C P.) 1 part
Gum tragacanth q. s.
This should be heated as above described.
A most interesting experiment is to make a selection of artificial
flowers, and, having brushed them over with glue or mucilage, dust
them with the powder from one of the balls made as described. If
the flowers are exposed to the sun a short time, they will emit a
phosphorescent light, each flower standing out in the darkness with
extreme brilliancy,--a striking and remarkable spectacle.
Canton’s phosphorus is easily made by calcining clean oyster-shells,
until they are perfectly white, in a crucible. The clearer and finer
portions should then be reduced to powder, and placed in layers with
alternate layers of flowers of sulphur in a crucible. Cover, and heat
to a dull redness for about half an hour, then allow to cool slowly.
Luminous “ink” or liquid can be made by placing a small piece of
phosphorus about as large as a pea in a test-tube with a small quantity
of olive oil; hold the tube in a water-bath until the oil becomes
heated, and the phosphorus liquefies; then shake it until the oil will
take up no more phosphorus, and, when it becomes clear, pour into
a bottle with a glass stopper. When it is to be used, take out the
stopper, and admit the air. The oil can be used with a brush, and in
the dark will appear luminous.
Water may be rendered phosphorescent by dissolving a small piece of
phosphorus in ether for several days in a glass-stoppered bottle; then
by immersing a piece of sugar in the solution, and placing it in water,
the latter becomes vividly phosphorescent. It should be remembered that
phosphorus and ether are both extremely dangerous, and experiments with
them should be conducted with care and judgment.
While this is a mere toy, luminous paint is of great value. It is
easily made, and can be applied to many purposes.
Schade of Dresden has quite recently patented an invention, which
enables him to produce paints that are luminous without affecting
the tint by day. This is accomplished, according to the inventor, as
follows:--
Zanzibar or Kauri copal is melted over a charcoal fire. Fifteen parts
of the melt are dissolved in 60 parts of French oil of turpentine, and
the filtered solution is mixed with 25 parts, previously heated and
cooled, pure linseed-oil. The varnish which is thus obtained, is used
in the following methods, in the manufacture of luminous paints, by
grinding between granite rolls in a paint-mill. Iron rolls should be
avoided, because particles of iron, which are liable to be detached,
would injure the luminous properties.
Varnishes, as they occur in commerce, generally contain lead or
manganese, which would destroy the phosphorescence of calcium sulphide.
_A pure white luminous paint_ is prepared by mixing 40 parts of the
varnish obtained in the abovedescribed process with 6 parts prepared
barium sulphate, 6 parts prepared calcium carbonate, 12 parts prepared
white zinc sulphide, and 36 parts good luminous calcium sulphide in
a proper vessel, to an emulsion, and then grinding it very fine in a
color-mill. For _red luminous paint_, 60 parts varnish are mixed with
8 parts prepared barium sulphate, 2 parts prepared madder lake, 6
parts prepared realgar (red arsenic sulphide), and 30 parts luminous
calcium sulphide, and treated the same as for white paint. For _orange
luminous paint_, 46 parts varnish are mixed with 17.5 parts prepared
barium sulphate, 1 part prepared Indian yellow, 1.5 parts prepared
madder lake, and 38 parts luminous calcium sulphide. For _yellow
luminous paint_, 48 parts varnish are mixed with 10 parts prepared
barium sulphate, 8 parts barium chromate, and 34 parts luminous calcium
sulphide. For _green luminous paint_, 48 parts varnish are mixed with
10 parts prepared barium sulphate, 8 parts chromium oxide green, and 34
parts luminous calcium sulphide.
_A blue luminous paint_ is prepared from 42 parts varnish, 10.2 parts
prepared barium sulphate, 6.4 parts ultramarine blue, 5.4 parts cobalt
blue, and 46 parts luminous calcium sulphide.
_A violet luminous paint_ is made from 42 parts varnish, 10.2 parts
prepared barium sulphate, 2.8 parts ultramarine violet, 9 parts
cobaltous arsenate, and 36 parts luminous calcium sulphide.
_For gray luminous paint_, 45 parts of the varnish are mixed with 6
parts prepared barium sulphate, 6 parts prepared calcium carbonate, O.5
parts ultramarine blue, 6.5 parts gray zinc sulphide.
_A yellowish-brown luminous paint_ is obtained from 48 parts varnish,
10 parts precipitated barium sulphate, 8 parts auri pigment, and 34
parts luminous calcium sulphide.
_Luminous colors for artists’_ use are prepared by using East India
poppy oil in the same quantity, instead of the varnish, and taking
particular pains to grind the materials as fine as possible.
_For luminous oil-color paints_, equal quantities of pure linseed oil
are used in place of the varnish. The linseed oil must be cold-pressed,
and thickened by heat. All the above luminous paints can be used in
the manufacture of colored papers, etc., if the varnish is altogether
omitted, and the dry mixtures are ground to a paste with water.
The luminous paints can also be used as _wax colors for painting on
glass_ and similar objects, by adding, instead of the varnish, ten per
cent more of Japanese wax, and one-fourth the quantity of the latter
of olive oil. The wax colors prepared in this way may also be used for
painting upon porcelain, and are then carefully burned without access
of air. Paintings of this kind can also be treated with water-glass.