place their eggs in a kind of burrow, which they dig like a rabbit. The bulfinch takes care to make the opening of her nest on the side least exposed to storm and rain. The loxia, or Phillipine sparrow, rolls its nest in a sort of spiral, and suspends it from a branch over still waters, to put it out of danger from reptiles. The hanging sparrow pursues a nearly similar plan; and we often see five or six of these nests on a single tree, like an ærial city. The sewer-bird has the address to sew a leaf detached from its stem to another, placed at the extremity of the branch, in this manner forming a kind of cradle, in which it deposits its tender young.

There are few spectacles of this sort more admirable than one which I have often witnessed. The bank-swallows of the Ohio and Mississippi valley scoop hundreds of little circular chambers from the hard and chalky banks of the rivers, always so chosen as that portions of rock, or of the solid bank, jut over their little municipal establishment, and defend it from rains and storms as a roof. Such are their social instincts, that, where circumstances admit, they seem to prefer attaching their habitations to those of men. I have noted two of these cities. In one, they were sheltered under the protecting roof of a naturalist, who cherished them. In another, they were settled on the south wall of an arsenal, and have continued to return to that place for a great number of years in succession. While recently surveying one, which contained some hundreds of habitations, I was informed that they had reared the greater part of this city in a single day; and it could not have contained less than as many hundred pounds of clay as there were families, all cemented firmly to the brick wall. The habitations were built in parallel curves, leaving streets between them. Nothing could exceed the neatness and exactness of the arch that was turned over them. They darted backwards and forwards into a hole, that seemed scarcely large enough to admit their bodies, with the rapidity of lightning. Each one invariably entered its own home, and all seemed quietness and peace.

What I most admired was, that under the shed of the

naturalist, conscious that they needed no protection from rain, none of their habitations were provided with arches; while on the naked and unsheltered wall of the arsenal, each one was so secured. Unhappily, instinct, as well as reason, is sometimes at fault. The last time I saw this city of swallows was after a great southern rain; for which, being at that season unusual, they seemed not to have been prepared. The clay had been softened, and whole portions of their city inundated and washed down. Hundreds of the young perished; and their parents, as they darted backward and forward over the ruins, uttered a sharp note of wailing, like the survivors of an inundated city.

Scarcely are the nests completed, when the females begin to lay. These little beings, before so flighty, inconstant, and vivid, become staid and faithful to their new charge. The females sing not; for in doing it, they would indicate the locality of their nests, and attract pursuit. But the male places himself on a neighbouring tree, too far from his mate to expose her to danger by his song; and there he soothes her maternal constancy with the sweetest symphony which his organs can utter. With two more facts I shall close these sketches of the preservative laws of animal instinct, abounding with details to an interminable extent.

Maternal tenderness having accomplished its first object, the beak of the young chick, enclosed in the hard shell, now warmed to life, is found armed with a bony point, which it uses, as a pick-axe, to break through the walls of its prison, Soon after the unfledged little animal has emerged to the light, this bony protuberance disappears.

Maternal tenderness, the preserving principle of the living universe, would have been unavailing without the impulsive instinct of love. As soon as the vernal restoration of nature is accomplished, the flower expands its beautiful and aromatic cup in a splendor to which the glory of Solomon was not to be compared. From the stamen it is fructified. The flower, having enjoyed its short hour of beauty and love, withers, and dies. At the same time the peacock spreads his proud plumage to the sun, and displays his splendor of

gold and diamonds. All the wood warblers put on their green, scarlet, and gold, the one color fading into the other with a downy softness, a changeable brilliancy, a richness, tempered with a delicacy which nature alone can lay on. Joy, pride, exultation, and love, show in every movement. They are wooing their loved ones in the branches; and their song, if we could interpret it, would be felt to possess all the poetry, ardor, and persuasion of love. But, as soon as the brief vernal hour of delight has past away, the purple, green, and gold fade. The peacock no longer expands his dazzling plumage. The bird of paradise loses its crest. The splendid combatants for their rival loves lay aside their collarette and their fierceness at the same time. They become sad and mute. The nightingale, instead of harmonious concerts, utters a croaking and plaintive note.

LECTURE X.

ELECTRICITY.

I SHALL now give you a brief introduction to the study of the natural philosopher. We will look at his instruments. With some he surveys the stars. With others he determines the weight of worlds. With some he extracts fire from the air, and with others from the water. He kindles his furnaces. From gold he produces you a fulminating powder, which kindles into a conflagration without fire, and explodes with far more noise and force than gunpowder. With silver he prepares a powder still more destructive and terrible. In his hollow glass globes, he creates a great number of invisible gases. Some burn, and others extinguish fire. One produces water. The slightest quantity of the third inflicts death. While he speaks to you, his hairs rise and bristle. He touches a tube of copper, and he is covered with brilliant sparks, and rays of light crown his head.

'Give me a lever and a pivot,' said Archimedes,' and I will move the world.' 'Give me matter and motion,' said Descartes, and I will make a world.'

With his magic lantern, the philosopher evokes shadows and spectres, invested with their sepulchral horrors. With phosphorus, he traces upon a tombstone a writing like that which the horror-struck Babylonish king saw inscribed on the wall in the midst of his high festival. By means of the burning mirror, he verifies all the reported prodigies said to have been wrought by Archimedes, and so long deemed incredible. Following the indications of Pherecides, he deems that he can foretell an earthquake. More daring than the famed Dædalus, soaring on his waxen pinions, with his balloon, he sails into the upper regions. Among catacombs and ruins, one genius has been found capable of decyphering the hieroglyphics and the mysteries of the Egyptian priests. Most of those arts, believed in ancient time, and, until very recently, by the moderns supposed to be wrought by magic, are now the trite and easy sports of the chemist and philosopher.

The Greek fire was discovered in the seventh century by Callinicus, a Greek engineer, and was lost from that time to the reign of Louis fifteenth of France. It was then discovered anew by Dupré. This terrible fire has also been prepared by Sir Humphrey Davy. Thenard composed it of charcoal, iron, and calcined potash. By the reunion of the iron and potash, a hydrate of potash is produced. The result is a black mass, very inflammable, which kindles as soon as wet. The historians of the early Turkish wars are eloquent in describing the dismay and ruin produced among the Christian crusaders, when the Turks cast this terrible fire into their fleet. Louis, the beloved, refused to avail himself of this terrific element.

-Man upon a world of dust, to which in a short time he returns, measures the immensity of the heavens, and declares the size, swiftness, and distance of the stars. Interrogate him, touching the structure and vegetation of a blade of grass, and he is silent. You see him amusing him

self with the magnet, with one end attracting needles and with the other repelling them. He delights his young family, by placing before them a number of beautiful waxen ducks in a large vessel of water. He seems to be able to impart life to them. He bids them swim from one side of the vessel to the other, and by a concealed movement of his hand, in which he holds a magnet, they appear to understand and obey his voice. He holds bread to them on one side of the vessel. A magnet is enclosed in the bread. The birds immediately swim to the side of the vessel, as if to devour the bread. To you, who comprehend the fact of magnetic action, this sport, which seems magic to the uninformed, appears puerile. To confound this pride of intellect, I ask you the cause of this action? You are silent. Yet this inexplicable power is the star of navigation, and was the key that unlocked the American hemisphere.

A little amber indicated the laws of the inexplicable phenomena of electricity, and taught that an iron rod would conduct lightning harmless to the ground. A few particles of vitrified sand form both a microscope, which enables us to discover myriads of inhabitants in a drop of water, and a telescope, by which we discover thousands of worlds in the depths of celestial space. The sea, which seemed to the ancients shoreless and illimitable, has become to us a short and measured highway. Hence the mechanic arts, which subserve our wants, supply our comforts, and embellish our abodes; and the abstract sciences, which supply the power of thought with food. With the simple elements of cyphers, lines, circles, and triangles, our engineers operate miracles in the construction of great public works, like the fabled results of the contests of the demigods, heaping Pelion upon Ossa. With a composition of black powder, cliffs are exploded, walls overthrown, and a new character given to the destructive art of war. The power of steam has been rendered capable of performing the labours of millions of hands, and of driving thousands of vessels against wind, current, and tide.

As electricity is one of the most surprising, inexplicable,