who bestows nothing in vain, has not therefore given it them. But, as the water which strongly refracts, serves them instead of the aqueous humor, they have been provided with a crystalline humor almost spherical, which, performing the operation of a burning glass, corrects the refracting power of the water, unites the dispersed rays, and concentrates them on the retina. We observe, too, that most of the classes of fishes have large eyes, a necessary circum stance to obviate the obscurity and density of the medium they inhabit. It was the examination of the structure of the eye which convinced the great ancient physician, Galen, that there was a God.

LECTURE XXVII.

COLORS.

I SHALL touch, in passing, upon the harmony of colors in the different climates. The sun paints the universe, as Raphael painted his pictures. Nothing is done in this work by chance. Every arrangement is not only in harmony with the vision and the wants of man, but even with the seasons and climates. The first flowers of spring are white. The apple-tree, pear-tree, wild-plum, crab-tree, dog-wood, and the prevalent flowering trees of our climate, show summits as white in their flowers as their recent snow-wreaths. This color is no caprice, but a wise foresight of nature. We have seen that white surfaces have the property of retaining heat, which easily escapes from colored surfaces. Thus nature supplies the warmth of the sun in the yet cool and uncertain temperature of the spring.

In proportion as summer advances, spring loses its snowy vesture of flowers; and the prevalent colors are blue, golden, and crimson. The shades change to brownish purple; and the flowers clothe themselves, if I may so say, in their

summer dress. Apply this remark to climates, and you will have under your eyes, the painting of the tropical countries of America and Africa, of countries which the sun inundates with his light; where we see the red flamingoes, the sparkling humming birds, the insects of gold and fire. Here we have the gorgeous spectacle of these rich shades in the midst of a gigantic nature, beside rapid streams of almost the breadth of seas, shading their shores with the lofty columns of the palm.

While the first spring-flowers of our temperate climates are of a brilliant white, those which grow in countries condemned to almost perpetual winter, on the contrary, are painted with the most glowing colors. The learned Patrin, who journeyed seven years in the dreary forests of Siberia, relates, that, one day as he was descending from the frozen summits of the mountain Altai, and as he reached the last bench which rose over the plain, watered by the majestic river Ob, he was struck with the most magnificent spectacle he had ever seen. He had left arid cliffs as old as the world, and snows and ices which were incessantly melted and renewed. On all sides, these desolate mountains were environed with storms, clouds, and snows. On a sudden an immense plain opened before the illustrious traveller, resplendent with the most vivid colors. Three species of vegetables entirely covered the surface. Not the least verdure was seen. The purple flower, of the iris of Siberia, formed the ground of this magnificent carpet. It was embroidered, in all its extent, with groups of hemerocalles, with flowers of gold and anemonies, with the narcissus of silvery brilliance. Sometimes the breath of the zephyr creates gentle undulations upon all these stalks. The varied colors are then so mingled and confounded, that the eye only sees waves of gold and purple which undulate under the brilliant sun. No hill, in the distance, bounds this rich plain. It spreads to the horizon, and seems to unite the sky and the earth with brilliant garlands.

In these frozen climates, many of the animals at the approach of winter gradually change to the color of snow.

This contrast between the color of vegetables and animals is another proof of the divine foresight. As it was necessary that the plants should be seen from a distance, they were pointed out, by their striking colors, to allure the animals that feed upon them. It was equally essential to the feebler animals that have a crowd of enemies, that, in procuring their food, they might glide over the snows confounded with them in the same color. Such is the case with the rabbits, the hares, and, in some countries, the squirrels and rats, and in the northern portions of Canada and New Britain most of the animals clothed with fur. The ermines of Siberia have no other defence than this change of color, and their caravans set forth in security by the light of the Aurora Borealis; while the foxes, bears, and wolves, are entirely black, brown, or blue.

St Pierre, in his Studies of Nature, avows that the reason of this contrast is unknown to him. Strange that this interpreter of nature had not divined, that nature has blanched the rabbits, partridges, and quails, only to conceal them from the eyes of their ferocious enemies; while the foxes, brown bears, and black wolves, armed with terrible teeth, resemble stalking shades, wandering, in strong contrast of color, upon the surface of the snows.

The colors and the forms of vegetables have exercised, even upon men, an influence equally pleasant and powerful. This influence is especially noted upon the Chinese. Their dress, buildings, and ornaments, are assimilated to the shades of coloring in their flowers, and the forms of their birds and animals. Their tents are modelled to the form of the inverted corolla of the tiger-lily of Japan. They have imitated the red and blue bells of the Faschia in their dress; and they wear bonnets, whose forms are borrowed from the campanulas of their meadows.

A fact equally remarkable, is, the harmony which existed between the ceremonies, the manners, and religion of the Peruvians, and the colors appropriate to the climate which they inhabited. It was natural that this simple people should worship the sun. The earth there yields gold, and

the planet of day shines with a radiance of glory. The flowers emit flame, as the capuchin; or assume the image of the sun, as the turnsol; or open only during the night, as the perfumed mirabilis. These observations extend even to the colors which adorn the sky. A green carpet is spread under our feet, an azure veil shines over our heads. The sun is also the painter of the clouds, and varies their aspects at every moment, changing them according to temperature and climate.

The sky of the highlands of Scotland shows inflamed clouds of a livid and copper color. The aspects of the firmament are stern and savage, like the heaths and mountains, and sombre as the genius of Ossian.

The horrible mythology of the Scandinavians seems to have been inspired by the sterility and harshness of the climate, the gloom of the sky, and the misery of the inhabitants. Every where the earth was ungrateful, and man was gloomy, and thirsted for the blood of man.

Between the tropics, the sky is of gold and flame.* Mountains of green and rose-colored mist seem to tower in the firmament, and are seen shifting their gorgeous-colored folds, and opening to view the varied play of light in the blue infinitude beyond. The sun, in his burning march, seems to create palaces in which to repose on his way.

Thin clouds, transparent vapors, and a pure sky cover the superb ruins of the Roman empire. Nothing can surpass the splendor of a summer evening in the American climates, when the sun is descending in his glory behind his towers of brass and his pavilions of purple. That would be a book at once of poetry, eloquence, and instruction, which should treat of the influence which the colors, and the varied aspects of the earth and sky, had upon the mythology and opinions of the ancient races of men. We should find the Olympus of Homer in the sky and plains of Greece, and the Elysian fields of Virgil in his own beautiful retreat in the vicinity of Naples.

LECTURE XXVIII.

OPTICAL ILLUSIONS.

You may consider this lecture an episode, in which I shall touch upon mirage, lands of mist, ærial illusions, and clouds assuming the aspects of animals, buildings, and works of art. 'I have observed,' says the traveller Patrin, 'in the sandy deserts of Asia and Africa, a phenomenon rendered singular by the illusive appearances which it presents. The traveller, in the midst of arid plains, imagines that he sees, at the distance of a few hundred steps, a vast extent of waters, whose shores sometimes appear covered with trees and verdure. Charmed with this agreeable and unexpected aspect, he presses onward in the hope of finding that refreshment and repose, which, in this scorching climate, he so greatly needs. But as he approaches in the direction of the object, it still retires before him, and finally vanishes.' This phenomenon, which has been called mirage and looming, has been observed by modern travellers in Egypt, and was formerly perceived by the army of Alexander in the deserts of Sagdiana, to the east of the Caspian sea, as we learn from the history of that conqueror. Quintus Curtius thus describes this appearance: 'When the fierceness of the sun heated these deserts, it might have been said, that the whole country assumed the aspect of a general inflammation. The sky was darkened by the vapors which arose from the burning soil, and the sandy plain had the appearance of a vast and profound sea.'

At the commencement of the last century, an English traveller, on his route to Pekin, who found himself, about the middle of October, in the sandy desert which separates Siberia from the frontiers of China, witnessed the same spectacle, which he describes in the following terms: