Atlantic Monthly, Volume 8, No. 47, September, 1861 by Various
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Various >> Atlantic Monthly, Volume 8, No. 47, September, 1861
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* * * * *
Modern pisciculture in some measure imitates, although, it does not
rival the ancient. Many methods have been devised in France and England
of breeding and nurturing the salmon, the trout, and other valuable
fish, which are annually becoming more scarce in all civilized
countries. But all this is on a far different principle from that
pursued at Rome. We follow pisciculture from necessity or economy,
because fish of certain kinds are yearly dying out, and to produce
a cheap food; but the Romans followed it as a luxury, or a childish
amusement, alone. And although our aldermen may sigh over a missing
Chelonian, as Crassus for his deceased eel, or the first salmon of the
season bring a fabulous price in the market, yet the time has long
passed when the gratification of appetite is alone thought of in
connection with Nature. We know that living creatures are to be studied,
as well as eaten; and that the faithful and reverent observation of
their idiosyncrasies, lives, and habits is as healthful and pleasing to
the mind as the consumption of their flesh is wholesome and grateful
to the body. The whole science of Zooelogy has arisen, with its simple
classifications and its vast details. The _vivaria_ of the Jardin des
Plantes rival those of the Colosseum in magnitude, and excel them in
object. Nature is ransacked, explored, and hunted down in every field,
only that she may add to the general knowledge. Museums collect and
arrange all the types of creative wisdom, from the simple cell to man.
Science searches out their extinct species and fossil remains, and tells
their age by Geology. The microscope pursues organic matter down into an
infinity of smallness, proportionately as far as the telescope traces it
upwards in the infinity of illimitable space. Last of all, though not
till long after the earth and the air had been seemingly exhausted,
the desire of knowledge began to push its way into the arcana of the
sea,--that hidden half of Nature, where are to be found those wonders
described by Milton at the Creation,--where, in obedience to the Divine
command,
"Be fruitful, multiply, and in the seas
And lakes and running streams the waters fill, ...
Forthwith the sounds and seas, each creek and bay,
With fry innumerable swarm, and shoals
Of fish, that with their fins and shining scales
Glide under the green wave in sculls that oft
Bank the mid sea: part single or with mate
Graze the sea-weed, their pasture, and through groves
Of coral stray, or sporting with quick glance
Show to the sun their waved coats dropt with gold,
Or in their pearly shells at ease attend
Moist nutriment, or under rocks their food
In jointed armor watch."
But no means were at hand to pursue these unknown creatures to their
unknown residences, and to observe their manners when at home. Single,
withered, and often mutilated specimens of minute fish, mollusks, or
radiata, in the museum, alone illustrated the mysteries of the deep sea.
Fish, to be sure, could be kept for longer or shorter periods in globes
of glass filled with water; but the more delicate creatures inevitably
perished soon after their removal from their mysterious abodes. Such
a passionate desire to "search Nature and know her secrets" finally
originated the idea of the Aquarium.
The term _vivarium_ was used among the ancients to signify many
things,--from the dens of the wild animals which opened under the
Colosseum, to an oyster-bed; and so now it may mean any collection of
living creatures. Hence it could convey no distinct idea of a marine
collection such as we propose to describe. The term _aqua_ was added to
express the watery element; but the compound _aqua-vivarium_ was too
clumsy for frequent employment, and the abbreviated word _aquarium_ has
come into general use.
Thus the real Aquarium is a water-garden and a menagerie combined,--and
aims to show life beneath the waters, both animal and vegetable, in
all the domestic security of its native home, and in all the beauty,
harmony, and nice adaptation of Nature herself. It is no sudden
discovery, but the growth of a long and patient research by naturalists.
"What happens, when we put half a dozen gold-fish into a globe? The
fishes gulp in water and expel it at the gills. As it passes through the
gills, whatever free oxygen the water contains is absorbed, and carbonic
acid given off in its place; and in course of time, the free oxygen of
the water is exhausted, the water becomes stale, and at last poisonous,
from excess of carbonic acid. If the water is not changed, the fishes
come to the surface and gulp atmospheric air. But though they naturally
breathe air (oxygen) as we do, yet they are formed to extract it from
the water; and when compelled to take air from the surface, the gills,
or lungs, soon get inflamed, and death at last puts an end to their
sufferings.
"Now, if a fish-globe be not overcrowded with fishes, we have only
to throw in a goodly handful of some water-weed,--such as the
_Callitriche_, for instance,--and a new set of chemical operations
commences at once, and it becomes unnecessary to change the water. The
reason of this is easily explained. Plants absorb oxygen as animals
do; but they also absorb carbonic acid, and from the carbonic add thus
absorbed they remove the pure carbon, and convert it into vegetable
tissue, giving out the free oxygen either to the water or the air, as
the case may be. Hence, in a vessel containing water-plants in a state
of healthy growth, the plants exhale more oxygen than they absorb, and
thus replace that which the fishes require for maintaining healthy
respiration. Any one who will observe the plants in an aquarium, when
the sun shines through the tank, will see the leaves studded with bright
beads, some of them sending up continuous streams of minute bubbles.
These beads and bubbles are pure oxygen, which the plants distil from
the water itself, in order to obtain its hydrogen, and from carbonic
acid, in order to obtain its carbon."[A]
[Footnote A:_The Book of the Aquarium_, by Sidney Hibbert.]
Thus the water, if the due proportion of its animal and vegetable
tenants be observed, need never be changed. This is the true Aquarium,
which aims to imitate the balance of Nature. By this balance the whole
organic world is kept living and healthy. For animals are dependent upon
the vegetable kingdom not only for all their food, but also for
the purification of the air, which they all breathe, either in the
atmosphere or in the water. The divine simplicity of this stupendous
scheme may well challenge our admiration. Each living thing, animal or
plant, uses what the other rejects, and gives back to the air what the
other needs. The balance must be perfect, or all life would expire, and
vanish from the earth.
This is the balance which we imitate in the Aquarium. It is the whole
law of life, the whole scheme of Nature, the whole equilibrium of our
organic world, inclosed in a bottle.
For the rapid evolution of oxygen by plants the action of sunlight is
required. That evolution becomes very feeble, or ceases entirely, in the
darkness of the night. Some authorities assert even that carbonic acid
is given off during the latter period. So, too, they claim that there
are two distinct processes carried on by the leaves of plants,--namely,
respiration and digestion: that the first is analogous to the same
process in animals; and that by it oxygen is absorbed from, and carbonic
acid returned to the atmosphere, though to a limited degree: and that
digestion consists in _the decomposition of carbonic acid by the green
tissues of the leaves under the stimulus of the light, the fixation of
solid carbon, and the evolution of pure oxygen_. The theory of distinct
respiration has been somewhat doubted by the highest botanical authority
of this country; but the theory of digestion is indisputable. And it is
no less certain that all forms of vegetation give to the air much more
free oxygen than they take from it, and much less carbonic acid, as
their carbonaceous composition shows. If fresh leaves are placed in
a bell-glass containing air charged with seven or eight per cent. of
carbonic acid, and exposed to the light of the sun, it will be found
that a large proportion of the carbonic acid will have disappeared, and
will be replaced by pure oxygen. But this change will not be effected in
the dark, nor by any degree of artificial light. Under water the oxygen
evolved from healthy vegetation can be readily collected as it rises, as
has been repeatedly proved.
Why carbonic acid is, to a limited degree, given off by the plant in the
night, is merely because the vital process, or the fixation of carbon
and evolution of oxygen, ceases when the light is withdrawn. The plant
is only in a passive state. Ordinary chemical forces resume their sway,
and the oxygen of the air combines with the newly deposited carbon to
reproduce a little carbonic acid. But this must be placed to the account
of decomposing, not of growing vegetation; for by so much as plants
grow, they decompose carbonic acid and give its oxygen to the air, or,
in other words, purify the air.
It has been found by experiment, that every six pounds of carbon in
existing plants has withdrawn twenty-two pounds of carbonic acid gas
from the atmosphere, and replaced it with sixteen pounds of oxygen gas,
occupying the same bulk. And when we consider the amount of carbon that
is contained in the tissues of living, and of extinct vegetation also,
in the form of peat and coal, we may have some idea of the vast body of
oxygen which the vegetable kingdom has added to the atmosphere.
And it is also to be considered, that this is the only means we know of
whereby free oxygen is given to supply the quantity constantly consumed
in respiration, combustion, and other vast and endless oxygen-using
processes. It follows, therefore, that animals are dependent upon plants
for their pure oxygen, as well as for their food. But the vegetable
kingdom might exist independently of the animal; since plants may derive
enough carbon from the soil, enriched by the decaying members of their
own race.
There is, however, one exception to the law that plants increase the
amount of oxygen in the air. During flowering and fruiting, the stores
of carbon laid up in the plant are used to support the process, and,
combining with the oxygen of the air, both carbonic acid and heat are
given off. This has been frequently proved. In large tropical plants,
where an immense number of blossoms are crowded together, the
temperature has risen twenty to fifty degrees above that of the
surrounding air.
As most of the aquatic plants are cryptogamous, or producing by spores,
and not by flowers, it seems probable that the evolution of carbonic
acid and heat is much less in degree in them, and therefore less in the
water than in the air. We may, therefore, venture to lay it down as a
general principle, that plants evolve free oxygen in water, when in
the sunlight, and remove the carbonic acid added to the water by the
respiration of the animals.
But since this is a digestive or nutritive process, it follows that
aquatic plants may derive much or all of their food from the water
itself, or the carbon in it, in the same manner as the so-called
air-plant, which grows without soil, does from the air. It is true, at
any rate, that, in the fresh-water aquarium, the river and brook plants
need no soil but pebbles; and that the marine plants have no proper
root, but are attached by a sort of sucker or foot-stalk to stones and
masses of rock. It is very easy to see, then, how the aquarium may
be made entirely self-supporting; and that, excepting for the larger
carnivorous fish, who exhaust in a longer or shorter period the minute
creatures on which they live, no external food is required.
A very simple experiment will prove the theory and practicability of the
aquarium. In a glass jar of moderate size was placed a piece of _Ulva
latissima_, or Sea-Lettuce, a broad-leaved, green, aquatic plant, and a
small fish. The mouth was closed by a ground glass stopper. The jar was
exposed to the light daily; the water was never changed; nor was the
glass stopper removed, excepting to feed the fish, once or twice a week,
with small fragments of meat. At the end of eight months both remained
flourishing: the fish was lively and active; and the plant had more than
half filled the bottle with fresh green leaves.
Any vessel that will hold water can, of course, be readily converted
into an aquarium. But as we desire a clear view of the contents at all
times, glass is the best material. And since glass globes refract the
light irregularly and magnify and distort whatever is within them, we
shall find an advantage in having the sides of the aquarium parallel and
the form rectangular. As the weight of the aquarium, when filled with
water, is enormous,--far more than we should at first imagine,--it
follows that it must be capable of resisting pressure both from above
and from within. The floor and stand, the frame and joints must be
strong and compact, and the walls of plate or thick crown glass. The
bottom should be of slate; and if it is designed to attach arches of
rock-work inside to the ends, they, too, must be of slate, as cement
will not stick to glass. The frame should be iron, zinc, or well-turned
wood; the joints closed with white-lead putty; the front and back of
glass. There is one objection to having the side which faces the light
of transparent glass, and that is that it transmits too much glare of
sunlight for the health of the animals. In Nature's aquarium the light
enters only from above; and the fish and delicate creatures have always,
even then, the shady fronds of aquatic plants or the shelter of the
rocks,--as well as the power of seeking greater depths of water, where
the light is less,--to protect themselves from too intense a sunshine.
It is, therefore, sometimes advisable to have the window side of the
aquarium made of glass stained of a green color. It is desirable that
all aquarial tanks should have a movable glass cover to protect them
from dust, impure gases, and smoke.
When we speak of an aquarium, we mean a vessel holding from eight to
thirty gallons of water. Mr. Gosse describes his larger tank as being
two feet long by eighteen inches wide and eighteen inches deep, and
holding some twenty gallons. Smaller and very pretty tanks may be
made fifteen inches long by twelve inches wide and twelve deep. Great
varieties in form and elegance may be adapted to various situations.
There are two kinds of aquaria, the fresh- and the salt-water: the one
fitted for the plants and animals of ponds and rivers; the other for the
less known tenants of the sea. They are best described as the River and
the Marine Aquarium, and they differ somewhat from each other. We shall
speak first of the fresh-water aquarium.
The tank being prepared, and well-seasoned, by being kept several weeks
alternately full and empty, and exposed to the sun and air, so that all
paint, oil, varnish, tannin, etc., may be wholly removed, the next thing
is to arrange the bottom and to plant it. Some rough fragments of rock,
free from iron or other metals that stain the water, may be built into
an arch with cement, or piled up in any shape to suit the fancy. The
bottom should be composed entirely of shingle or small pebbles, well
washed. Common silver sand, washed until the water can be poured through
it quite clear, is also suitable.
Mould, or soil adapted to ordinary vegetation, is not necessary to
the aquatic plants, and is, moreover, worse than useless; since it
necessitates the frequent changing of the water for some time, in order
to get rid of the soluble vegetable matter, and promotes the growth of
Confervae, and other low forms of vegetation, which are obnoxious.
Aquatic plants of all kinds have been found to root freely and flourish
in pebbles alone, if their roots be covered. The plants should be
carefully cleared of all dead parts; the roots attached to a small
stone, or laid on the bottom and covered with a layer of pebbles and
sand.
The bottom being planted, the water may be introduced through a
watering-pot, or poured against the side of the tank, so as to avoid any
violent agitation of the bottom. The water should be pure and bright.
River-water is best; spring-water will do, but must be softened by the
plants for some days before the fishes are put in.
Sunshine is good for the tank at all seasons of the year. The
fresh- requires more than the salt-water aquarium. The amount of
oxygen given off by the plants, and hence their growth and the
sprightliness of the fishes, are very much increased while the sun
is shining on them.
In selecting plants for the aquarium some regard is to be paid to the
amount of oxygen they will evolve, and to their hardiness, as well as to
their beauty. When it is desired to introduce the fishes without waiting
long for the plants to get settled and to have given off a good supply
of oxygen, there is no plant more useful than the _Callitricke_, or
Brook Star-wort. It is necessary to get a good supply, and pick off the
green heads, with four or six inches only of stem; wash them clean,
and throw them into the tank, without planting. They spread over the
surface, forming a rich green ceiling, grow freely, and last for months.
They are continually throwing out new roots and shoots, and create
abundance of oxygen. Whenever desired, they can be got rid of by simply
lifting them out.
The _Vallisneria_, or Tape-Grass, common in all our ponds, is essential
to every fresh-water tank. It must be grown as a bottom-plant, and
flourishes only when rooted. The _Nitella_ is another pleasing variety.
The _Ranunculus aquatilis_, or Water-Crowfoot, is to be found in almost
every pond in bloom by the middle of May, and continues so into the
autumn. It is of the buttercup family, and may be known as a white
buttercup with a yellow centre. The floating leaves are fleshy; the
lower ones finely cut. It must be very carefully washed, and planted
from a good joint, allowing length enough of stem to reach the surface.
Some of the blossom-heads may also be sprinkled over the surface, where
they will live and bloom all through the summer. The _Hydrocharis_,
or Frog's-Bit, and the _Alisma_, or Water-Plantain, are also easily
obtained, hardy and useful, as well as pleasing. Many rarer and more
showy varieties may be cultivated; we have given only the most common
and essential. All the varieties of _Chara_ are interesting to the
microscopist, as showing the phenomenon of the circulation of the sap,
or Cyclosis.
Of the living tenants of the aquarium, those most interesting, as well
as of the highest organization, are the fishes. And among fishes, the
family of the _Cyprinidae_ are the best adapted to our purpose; for we
must select those which are both hardy and tamable. _Cyprinus gibelio_,
the Prussian Carp, is one of the best. It will survive, even if the
water should accidentally become almost exhausted of oxygen. It may
be taught, also, to feed from the hand. None of the carp are very
carnivorous. _Cyprinus auratus_, or the Gold-fish, is one of the most
ornamental objects in an aquarium. But the Minnow, _C. phoxinus_, is the
jolliest little fish in the tank. He is the life of the collection, and
will survive the severest trials of heat and cold. The Chub, a common
tenant of our ponds, is also a good subject for domestication. The
Tench and Loach are very interesting, but also very delicate. Among the
spiny-finned fishes, the Sticklebacks are the prettiest, but so savage
that they often occasion much mischief. For a vessel containing
twelve gallons the following selection of live stock is among those
recommended: Three Gold Carp, three Prussian Carp, two Perch, four
large Loach, a dozen Minnows, six Bleak, and two dozen Planorbis. Some
varieties of the Water-Beetles, or Water-Spiders, which the fishes
do not eat, may also well be added. The Newt, too, is attractive and
harmless.
All may go on well, and the water remain clear; but after the tank has
been established several weeks, the inner sides of the glass will show a
green tinge, which soon increases and interferes with the view. This is
owing to the growth of a minute confervoid vegetation, which must be
kept down. For this purpose the Snail is the natural remedy, being the
ready scavenger of all such nuisances. Snails cling to the sides, and
clean away and consume all this vegetable growth. The _Lymnea_ is among
the most efficient, but unfortunately is destructive, by eating holes
in the young fronds of the larger plants, and thus injuring their
appearance. To this objection some other varieties of snail are not
open. The _Paludina_ and _Planorbis_ are the only kinds which are
trustworthy. The former is a handsome snail, with a bronze-tinted,
globular shell; the latter has a spiral form. These will readily reduce
the vegetation. And to preserve the crystal clearness of the water, some
Mussels may be allowed to burrow in the sand, where they will perform
the office of animated filters. They strain off matters held in
suspension in the water, by means of their siphons and ciliated gills.
With these precautions, a well-balanced tank will long retain all the
pristine purity of Nature.
Specimens for the river aquarium may be readily obtained in almost
any brook or pool, by means of the hand-net or dredge. It will be
astonishing to see the variety of objects brought up by a successful
haul. Small fish, newts, tadpoles, mollusks, water-beetles, worms,
spiders, and spawn of all kinds will be visible to the naked eye; while
the microscope will bring out thousands more of the most beautiful
objects.
A very different style of appearance and of objects distinguishes the
Salt-water or Marine Aquarium.
As the greater part of the most curious live stock of the salt-water
aquarium live upon or near the bottom, so the marine tank should be more
shallow, and allow an uninterrupted view from above. Marine creatures
are more delicately constituted than fresh-water ones; and they demand
more care, patience, and oversight to render the marine aquarium
successful.
Sea-sand and pebbles, washed clean, form the best bottom for the
salt-water aquarium. It must be recollected that many of the marine
tenants are burrowers, and require a bottom adapted to their habits.
Some rock-work is considered essential to afford a grateful shelter and
concealment to such creatures as are timid by nature, and require a spot
in which to hide: this is true of many fishes. Branches of coral, bedded
in cement, may be introduced, and form beautiful and natural objects, on
which plants will climb and droop gracefully.
Sea-water dipped from the open sea, away from the mouths of rivers,
is, of course, the best for the marine aquarium. If pure, it will bear
transportation and loss of time before being put into the tank. It may,
however, not always be possible to get sea-water, particularly for the
aquarium remote from the seaboard, and it is therefore fortunate that
artificial sea-water will answer every purpose.
The composition of natural sea-water is, in a thousand parts,
approximately, as follows: Water, 964 parts; Common Salt, 27; Chloride
of Magnesium, 3.6; Chloride of Potassium, 0.7; Sulphate of Magnesia,
(Epsom Salts,) 2; Sulphate of Lime, 1.4; Bromide of Magnesium, Carbonate
of Lime, etc., .02 to .03 parts. Now the Bromide of Magnesium, and
Sulphate and Carbonate of Lime, occur in such small quantities, that
they can be safely omitted in making artificial seawater; and besides,
river and spring water always contain a considerable proportion of lime.
Therefore, according to Mr. Gosse, we may use the following formula: In
every hundred parts of the solid ingredients, Common Salt, 81 parts;
Epsom Salts, 7 parts; Chloride of Magnesium, 10 parts; Chloride of
Potassium, 2 parts; and of Water about 2900 parts, although this must be
accurately determined by the specific gravity. The mixture had better
be allowed to stand several days before filling the tank; for thus the
impurities of the chemicals will settle, and the clear liquor can be
decanted off. The specific gravity should then be tested with the
hydrometer, and may safely range from 1026 to 1028,--fresh water being
1000. If a quart or two of real sea-water can be obtained, it is a very
useful addition to the mixture. It may now be introduced into the tank
through a filter. But no living creatures must be introduced until the
artificial water has been softened and prepared by the growth of the
marine plants in it for several weeks. Thus, too, it will be oxygenated,
and ready for the oxygen-using tenants.
It is a singular fact, that water which has been thus prepared, with
only four ingredients, will, after being a month or more in the
aquarium, acquire the other constituents which are normally present in
minute quantities in the natural sea-water. It must derive them from the
action of the plants or animals, or both. Bromine may come from sponges,
or sea-wrack, perhaps. Thus artificial water eventually rights itself.
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