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.

The tank, having been prepared and seasoned with the same precaution used for the river aquarium, and having a clear bottom and a supply of good water, is now ready for planting. Many beautifully colored and delicately fringed Algæ and Sea-Wracks will be found on the rocks at low tide, and will sadly tempt the enthusiast to consign their delicate hues to the aquarium. All such temptations must be resisted. Green is the only color well adapted for healthy and oxygenating growth in the new tank. A small selection of the purple or red varieties may perhaps be introduced and successfully cultivated at a

later day, but they are very delicate; while the olives and browns are pretty sure to die and corrupt the water. It must be remembered, too, that the Alga are cryptogamous, and bear no visible flowers to delight the eye or fancy. Of all marine plants, the Ulva latissima, or Sea-Lettuce, is first and best. It has broad, light-green fronds, and is hardy and a rapid grower, and hence a good giver of oxygen. Next to this in looks and usefulness comes the Enteromorpha compressa, a delicate, grass-like Alga. After a while the Chondrus crispus, or common Carrageen Moss, may be chosen and added. These ought to be enough for some months, as it is not safe to add too many at once. Then the green weeds Codium tomentosum and Cladophora may be tried; and, still later, the beautiful Bryopsis plumosa. But it is much better to be content with a few Ulvæ, and others of that class, to begin with; for a half dozen of these will support quite a variety of animal life.

After a few hardy plants are well set, and thriving for a week or two, and the water is clear and bubbly with oxygen, it will be time to look about for the live stock of the marine aquarium. Fishes, though most attractive, must be put in last; for as they are of the highest vitality, so they require the most oxygen and food, and hence should not be trusted until everything in the tank is well a-going.

The first tenants should be the hardy varieties of the Sea-Anemones, or Actiniæ, — which are Polyps, of the class Radiata. The Actinia mesembryanthemum is the common smooth anemone, abounding on the coast, and often to be found attached to stones on the beach. "When closed," says Mr. Hibbert, "it has much resemblance to a ripe strawberry, being of a deep chocolate color, dotted with small yellow spots. When expanded, a circle of bright blue beads or tubercles is seen within the central opening; and a number of coral-like fingers or tentacles unfold from the centre, and spread out on all sides." It remains expanded for many

days together, if the water be kept pure; and, having little desire for locomotion, stays, generally, about where it is placed. It is a carnivorous creature, and seeks its food with its ever-searching tentacles, thus drawing in fishes and mollusks, but, most frequently, the minute Infusoria. Like other polyps, it may be cut in two, and each part becomes a new creature. It is a very pretty and hardy object in the aquarium. There are many varieties, some of which are very delicate, as the Actinia anguicoma, or Snaky-locked Anemone, and the pink and brown Actinia bellis, which so resembles a daisy. Others, as the Actinia parasitica, are obtainable only by deep-sea dredging; "and, as its name implies, it usually inhabits the shell of some defunct mollusk. And more curious still, in the same shell we usually find a pretty crab, who acts as porter to the anemone. He drags the shell about with him like a palanquin, on which sits enthroned a very bloated, but gayly-dressed potentate, destitute of power to move it for himself."*

The Actinia gemmacea, or Gemmed Anemone, the Actinia crassicornis, and the Plumose Anemone are all beautiful, but tender varieties.

The Anemones require but little care; they do not generally need feeding, though the Daisy and Plumose Anemone greedily take minced mutton, or oyster. But, as a rule, there are enough Infusoria for their subsistence; and it is safer not to feed them, as any fragments not consumed will decay, and contaminate the water.

Next in order of usefulness, hardiness, and adaptability to the new aquarium, come the Mollusks. And of these, Snails and Periwinkles claim our respectful attention, as the most faithful, patient, and necessary scavengers of the confervoid growths, which soon obscure the marine aquarium.

"It is interesting," says Mr. Gosse, "to watch the business-like way in which the Periwinkle feeds. At very regular intervals, the proboscis, a tube with thick

Hibbert's Book of the Aquarium.

fleshy walls, is rapidly turned inside out to a certain extent, until a surface is brought into contact with the glass having a silky lustre; this is the tongue; it is moved with a short sweep, and then the tubular proboscis infolds its walls again, the tongue disappearing, and every filament of Conferva being carried up into the interior, from the little area which had been swept. The next instant, the foot meanwhile having made a small advance, the proboscis unfolds again, the tongue makes another sweep, and again the whole is withdrawn; and this proceeds with great regularity. I can com pare the action to nothing so well as to the manner in which the tongue of an ox licks up the grass of the field, or to the action of the mower cutting swath after swath."

Of Crustacea, the Prawns and the smaller kinds of Crabs may be admitted to the aquarium, though but sparingly. They are rude, noisy, quarrelsome, and somewhat destructive,-but, for the same reason, amusing tenants of the tank.

All are familiar with the mode in which the Soldier or Hermit Crab takes possession of and lives in the shells of Whelks and Snails. Poorly protected behind by Nature, the homeless crab wanders about seeking a lodging. Presently he meets with an empty shell, and, after probing it carefully with his claw to be sure it is not tenanted, he pops into it back foremost in a twinkling, and settles himself in his new house. Often, too, he may be seen balancing the conveniences of the one he is in and of another vacant lodging he has found in his travels; and he even ventures out of his own, and into the other, and back again, before being satisfied as to their respective merits. In all these manoeuvres, as well as in his daily battles with his brethren, he is one of the drollest of creatures.

As we advance in our practice with the aquarium we may venture to introduce more delicate lodgers. Such are the beautiful family of the Annelida: the Serpula, in his dirty house; and the Terebella, most ancient of masons, who lays

the walls of his home in water-proof ce

ment.

The great class of Zoöphytes can be introduced, but many varieties of them will be found already within the aquarium, in the company of their more bulky neighbors. These peculiar creatures, or things, form the boundary where the last gleam of animal life is so feeble and flickering as to render it doubtful whether they belong to the animal or vegetable kingdom. Agassiz calls them Protozoa, Primary Existences. Some divide them into two great classes, namely: the Anthozoa, or Flower-Life; and the Polyzoa, or Many-Life, in which the individuals are associated in numbers. They are mostly inhabitants of the water; all are destitute of joints, nerves, lungs, and proper blood-vessels; but they all possess an irritable system, in obedience to which they expand or contract at will. Among the Anthozoa are the Anemones; among the Polyzoa are the Madrepores, or CoralBuilders, and many others. Many are microscopic, and belong to the class of animalcules called Infusoria.

A very remarkable quality which the Infusoria possess one very useful for the aquarium, and one which would seem to settle their place in the vegetable kingdom - is that they exhale oxygen like plants. This has been proved by Liebig, who collected several jars of oxygen from tanks containing Infusoria only.

A piece of honeycomb coral (Eschara foliacea) is easily found, and, when well selected and placed in the aquarium, may continue to grow there by the labors of its living infusorial tenants: they are not unworthy rivals of the Madrepores, or deep-sea coral-builders of warmer latitudes. The walls of its cells are not more than one-thirtieth of an inch in thickness, and each cell has its occupant. So closely are they packed, that in an area of one-eighth of an inch square the orifices of forty-five cells can be counted. As these are all double, this would give five thousand seven hundred and sixty cells to the square inch. Now a moderate-sized specimen will afford, with all its

convolutions, at least one hundred square inches of wall, which would contain a population population of five hundred and seventysix thousand inhabitants,— a very large city. So says Mr. Gosse. We cannot forbear, with him, from quoting Montgomery's lines on the labors of the coralworms, which modern science has enabled us to study in our parlors.

"Millions on millions thus, from age to age, With simplest skill, and toil unweariable, No moment and no movement unimproved, Laid line on line, on terrace terrace spread, To swell the heightening, brightening, gradual mound,

By marvellous structure climbing towards the day.

Each wrought alone, yet all together
wrought,

Unconscious, not unworthy instruments,
By which a hand invisible was rearing
A new creation in the secret deep.

. I saw the living pile ascend,
The mausoleum of its architects,
Still dying upwards as their labors closed;
Slime the material, but the slime was turned
To adamant by their petrific touch:
Frail were their frames, ephemeral their
lives,

Their masonry imperishable."

The deep-sea soundings taken recently for the Atlantic telegraph have demonstrated the existence of organic life even at the bottom of the ocean. Numerous living Infusoria have been brought to the light of day, from their hidden recesses, by the lead. "Deeper than ever plummet sounded" before these latter days, there exist myriads of minute creatures, and of Algæ to furnish their food. It is an unanswered problem, How they can resist the enormous pressure to which they must be there subjected, amounting, not infrequently, to several tons to the square inch. And still another point of interest for us springs from this. It is an inquiry of practical importance to the aquarian naturalist, How far the diminished pressure which they meet with in the tank, on being transferred from their lower homes to the aquarium, may influence their viability. May not some of the numerous deaths in the marine tank be reasonably attributed to this lack of pressure?

What a difference, too, has Nature established, in the natural power to resist pressure, between those creatures which float near the surface and those which haunt the deeper sea! The Jelly-fish can live only near the top of the water, and, floating softly through a gentle medium, is yet crushed by a touch; while the Coralbuilder bears the superincumbent weight of worlds on his vaulted cell with perfect impunity.

Another important question is, How far alteration in the amount of light may affect the more delicate creatures. What fishes do without light has been solved by the darkness of the Mammoth Cave, the tenants of whose black pools are eyeless, evidently because there is nothing to see. The more deeply located Infusoria and Mollusks must dwell in an endless twilight; for Humboldt has found, by experiment, that at a depth one hundred and ninety-two feet from the surface the amount of sunlight which can penetrate is equal only to one-half of the light of an ordinary candle one foot distant.

Thus ever in gloom, yet in a state of constant safety from storms and the agitations of the upper air, the thousand forms of low organic life and cryptogamic vegetation live and thrive in peace and quietness.

The perfect transparency, elegant form, and graceful navigation of the Medusœ, or Jelly-fishes, render them much admired in their native haunts, and prized for the aquarium. But they are very deli❤ cate. How beautiful and remarkable are these headless Discophori, as they float, and propel themselves with involutions of their disks and gently trailing tentacles, and the central peduncle hanging far below, like the clapper of a transparent bell! And yet these wonders are but so much sea-water, inclosed in so slight a tissue that it withers in the sun, and leaves only a minute spot of dried-up gelatinous substance behind.

Finally come the Fishes, many of which are of similar genera to those recommended for the fresh-water tank. The Black Goby is familiar, tamable, but voracious; the Gray Mullet is very hardy, but also rather savage; the Wrasses are some of the most showy fish, called in some parts of the country Cunners, and of these, the Ancient Wrasse, (Labrus maculatus,) covered with a network of vermilion meshes on a brown and white ground, is the most elegant.

And the pearl-shells spangle the flinty

common error of trying too many things at once. The aquarium must be built up slowly and tentatively, object by object: plants first, and of the simplest kinds; and not until they are well settled, and the water beaded with oxygen bubbles, should we think of introducing living creatures, and even then only the hardier kinds of actinias, mollusks, and crabs. All delicate animals must be intrusted one by one to their new home, and carefully watched for deaths and decay, which, whether arising from dead plants or animals, ruin everything very quickly, unless they be promptly removed. For sulphuretted hydrogen, even in very minute quantities, is sure death to all these little creatures.

The emanations from paint and putty are often fatal in new tanks. Several weeks' exposure to water, air, and sunlight is necessary to season the new-made aquarium. Of equal consequence is it that the water be absolutely pure; and if brought from the sea, care must be exercised about the vessel containing it. Salt acts upon the glazing of earthen ware of some kinds. Stone or glass jars are safest. New oak casks are fatal from the tannin which soaks out; fir casks are safe and good. So delicate and sensitive are the minute creatures which people the sea, that they have been found dead on opening a cask in which a new oak bung was the only source of poison. And no wonder; for a very slight proportion of tannic acid in the water corrugates and stiffens the thin, smooth skin of the anemone, like the tanning of leather.

A certain natural density of the seawater must also be preserved, ranging between no wider limits than 1026 and 1028. And in the open tank evaporation is constantly deranging this, and must be met by a supply from without. As the pure water alone evaporates, and the salts and earthy or mineral constituents are left behind, two things result: the water remaining becomes constantly more dense; and this can be remedied only by pure fresh water poured in to restore the equilibrium. Hence the marine aquarium must be replenished with fresh water, until the proper specific gravity, as indicated by the hydrometer, is restored.

The aquarium may be found some morning with a deep and permanent green stain discoloring the water. This unsightly appearance is owing to the simultaneous development of the spores of multitudes of minute Algae and Confervæ, and can be obviated by passing the water through a charcoal filter. When any of the fishes give signs of sickness or suffocation, by coming to the surface and gulping air, they may be revived by having the water aërated by pouring it out repeatedly from a little elevation, or by a syringe. The fishes

are sometimes distressed, also, when the room gets too warm for them. A temperature of 60° is about what they require. And they will stand cold, many of them, even to being frozen with the water into ice, and afterwards revive.

The degree of light should be carefully regulated by a stained glass side, or a shade. Yet it must be borne in mind that sunlight is indispensable to the free evolution of oxygen by the plants. And when the sun is shining on the water, all its occupants appear more lively and the fishes seem intoxicated - as they doubtless are with oxygen.

A novice is apt to overstock his aquarium. Not more than two moderate-sized fishes to a gallon of water is a safe rule. Care, too, must be taken to group together those kinds of creatures which are not natural enemies, or natural food for each other, or a sad scene of devastation and murder will ensue.

Cleansing cannot be always intrusted to snails. But the sides may be scrubbed with a soft swab, made of cotton or wick-yarn. Deaths will occasionally take place; and even suicide is said to be resorted to by the wicked family of the Echinoderms.

To procure specimens for the aquarium requires some knack and knowledge. The sea-shore must be haunted, and even the deep sea explored. At the extreme low-water of new or full moon tides, the rocks and tide-pools are to be zealously hunted over by the aquarian naturalist. Several wide-mouthed vials and stone jars are necessary; and we would repeat, that no plant should be taken, unless its attachment is preserved. It is often a long and difficult job to get some of the Algae with their tender connections unsevered from the hard rock, which must be chipped away with the chisel, and often with the blows of the hammer deadened by being struck under water. It is by lifting up the overhanging masses of slimy fuci, tangles, and sea-grass, that we find the delicate varieties, as the Chondrus with its metallic lustre, and the red Algae, or the stony Corallina,