The depth of lakes is sometimes very great, particularly in mountainous districts, as, for example, the Lake of Geneva, has attained the enormous depth of 161 fathoms (966 feet). Some lakes in Sweden and elsewhere are said to have double bottoms, as their depth, when taken at different times, varies exceedingly; but this phenomenon is supposed to arise from the interwoven roots of trees becoming incrusted, and being suspended near the bottom of the lake, as this kind of bottom would naturally rise and fall according to circumstances.
The quality of the water of lakes differs exceedingly: those which have a river running through them are always fresh; but those which have no outlet are invariably salt. In the Dead Sea the waters contain eight times as much salt as the common sea. The water of some lakes abounds in soda, as is the case with the Natron lakes in Lower Egypt; and other lakes produce a pitchy substance, as for example the Dead Sea. In the Island of Trinidad there is a lake of this kind, upon the surface of which floats an enormous quantity of bitumen, fit for naval purposes. What is called bog iron is a deposition from the waters of lakes which are impregnated with iron, and tuffa and sinter are deposits from lakes that are fed by calcareous springs.
ASIATIC LAKES.
The most remarkable lake in the world is what is generally called the Dead Sea. It lies in Palestine, and is about fifty miles in length and twelve or thirteen in breadth. It is surrounded by lofty mountains, and receives the waters of the river Jordan, and of some other streams, though it has no visible outlet. Copious evaporation, caused by subterraneous heat, is supposed, however, to supply the place of one. The water of the lake is clear and limpid, but excessively salt, and of greater specific gravity than any other water that has yet been discovered. The proportion of salt varies, but it appears generally to amount to nearly fifty per cent, and this enormous proportion of salt explains the difficulty that exists in diving into the waters, and the resistance they offer to the wind; so that it is quite true no one can bathe in its waters, and no winds ruffle its surface.
Another peculiarity in this lake is, that there is always a great quantity of the bituminous and inflammable substance called asphaltum, or mineral pitch, floating on its surface, which rises from the bottom of the lake in a melted state, and is condensed by the water. There is also another kind of pitch found on the shore, which, as well as the asphaltum, is used in embalming bodies, and for various other purposes. This lake is called the Dead Sea from the total want of motion in its waters; but the stories that are told of the vapours that arise from it being destructive to animal and vegetable life, are quite fallacious.
The Caspian Sea is the largest lake in the Eastern Hemisphere, as it is about 650 miles in length, and from 100 to 250 miles in breadth. The water is less salt than that of the ocean, but it is bitter, and of a dingy yellow colour, without ebb or flow. In some places it is exceedingly deep, but as it abounds in shallows, its navigation is extremely difficult. The level of this lake is 375 feet below that of the ocean; and, though several large rivers flow into it, it has no outlet.
AMERICAN LAKES.
The principal of these are the five lakes of Canada, viz. Superior, Huron, Ontario, Erie, and Michigan.
Lake Superior is not only the largest lake in America, but the largest expanse of fresh water in the known world. It is also remarkable for the level of its waters being several hundred feet higher than those of the river St. Lawrence, of which it may be said to be the head. The circumference of this lake is estimated at about 1,500 miles, and its waters are remarkably clear. "When it was calm," a traveller observes, "and the sun shone bright, I could sit in my canoe, where the depth was upwards of six fathoms, and could plainly see huge piles of stone at the bottom. The water at this time was pure and transparent as the air, and my canoe seemed as if it hung suspended in that element. It was impossible to look attentively through this limpid medium at the rocks beneath for even a few minutes, without feeling the head swim, and the eyes no longer able to view the dazzling scene." This occurred in the month of July, and although the surface of the water, from the heat of the atmosphere, was warm, still, on letting down a cup to the depth of about a fathom, the water drawn thence was so extremely cold, that when taken into the mouth it had the effect of ice. Lake Superior is said to receive the waters of nearly forty rivers, one of which, just before it enters the lake, has a perpendicular fall of more than 600 feet, through a very narrow channel. The lake contains several islands, two of which are of considerable size. It has only one passage for the discharge of its waters, viz. St. Mary's Strait, which communicates with Lake Huron.
Lake Huron is about 1,000 miles in circumference; its shape is nearly triangular, and it is united to Lake Superior by St. Mary's Strait, which is forty miles in length, and has in its course some of those falls which are called in America, Rapids, because the waters pass along a sloping bottom, and do not fall perpendicularly. This lake communicates on one side with Lake Erie, from which it is distant about eighty miles, and on the other side with Lake Michigan; and it has on its north side a long island about 100 miles in length, and only eight broad, which is supposed by the Indians to be the abode of spirits.
Lake Erie is nearly 300 miles in its longest part. Its navigation is more dangerous than that of the other lakes, from its numerous head-lands, which project into the lake; and when sudden storms arise, boats and canoes are frequently lost by being dashed against them.
Lake Michigan is long and narrow, and it communicates with Lake Huron by a strait about forty miles wide, called the Grand Traverse.
Lake Ontario is the smallest of these lakes, but even its circumference is about 600 miles. It communicates with Lake Erie through the river Niagara, which, after flowing nearly forty miles, discharges itself by its celebrated falls into Lake Ontario.
The Wenham Lake, from which so much ice has been brought to England, is of comparatively small size, in the State of Massachusetts.
EUROPEAN LAKES.
These lakes, though very inferior in size to those of America, have several very remarkable peculiarities.
Lake Ladoga, in the western part of Russia, which is the largest European lake, is 150 miles long, and ninety in breadth. It is, however, full of quicksands, which are constantly moved from place to place by the frequent storms to which the lake is subjected. This led Peter the Great to cause a canal, seventy miles long, to be cut from the lake to the sea; and, as everything is done in Russia by the military, the czar devoted a regiment of soldiers to the care of the lake and its canal; and soldiers for this purpose are still stationed along its banks.
Lake Onega is another large lake in Russia, the waters of which, though they are not salt, are frequented by seals.
There are several other large lakes in the north of Europe, particularly Lake Mäler, in Sweden, which is said to contain 1,290 islands.
The most interesting lakes of Europe are, however, the Lake of Geneva, the Lake of Cirknitz, in Illyria, and Lago Maggiore, in Italy.
The Lake of Geneva has already been mentioned to be of enormous depth. In summer it has a movement which resembles the ebbing and flowing of the tide; and, as its waters are extremely clear, the waters of the Rhone, which are very muddy, may be distinctly traced through it for two or three miles.
The Lake of Cirknitz is about eight miles in length, and two in breadth. "In the beginning of June, its waters disappear through several fissures in its basin, and the peasants immediately begin to cultivate its bottom, or to pasture their herds on the rich herbage which its oozy bed soon produces." The crop is removed about the end of September, and towards the middle of October the waters return, spouting up with great force through several apertures in the earth. With these waters various kinds of fish appear, and with them is seen the curious creature called the Syren (Anguina proteus), which is also found in the river which runs through the Cavern of Adelsberg, and which is thus supposed to prove that there is a communication between that river and the lake. The lake may, however, communicate with some other subterranean river, as it is surrounded by limestone hills, which are known to be hollowed out into vast caverns; and these caverns are supposed to be the receptacles of subterraneous rivers, which, when augmented by autumnal rains, may overflow into a channel communicating with the Lake of Cirknitz, and when the sources of these floods fail, it seems probable that the waters of the lake may retreat to supply the deficiency. Other lakes of this kind are said to occur in Dalmatia.
Lago Maggiore is in the Duchy of Milan, and though it is not more than six miles in breadth, it is upwards of sixty in length. It has on both sides hills covered with vineyards, and with several fine cascades falling from their sides. In one part, where the lake becomes considerably wider, are the two celebrated islands named Isola Bella and Isola Madre, which have been compared to two pyramids of confectionary. These, and two other islands in the lake, are generally called the Borromean Isles, as they were formed in their present state by one of the Counts Borromeo. This nobleman, in the year 1671, finding that there were several naked rocks in the lake, caused three of them to be covered with garden soil, building terraces to retain the soil in its proper place. Thus arose Isola Bella and Isola Madre, on which are splendid gardens and palaces; but the third island, Isola dei Piscatori, having had less pains bestowed upon it, is only the abode of fishermen. There is also a fourth island, called L'Isolino, which is much smaller than the others. The Isola Madre, which abounds in pheasants, lies in the middle of the lake: it consists of seven terraces, planted with myrtles, oleanders, laurels, and many other ornamental trees and shrubs. "The Isola Bella is loaded with artificial ornaments. It contains a handsome palace of four stories, which lies near the shore, and is occupied, for some months in the year by the Count Borromeo. By means of the Grotte Terrene, it communicates with the gardens, which are laid out in the French taste, upon ten terraces, rising above each other, and narrowing in proportion to their elevation. The whole has the appearance of a truncated pyramid, on the top of which stands a colossal unicorn, the armorial ensign of the Borromei. Orange, citron, and lemon trees, united by fine hedges, or forming arbours, breathe their fragrance; lofty laurels form a little grove; myrtles and cypress are to be seen, together with pomegranate trees, the fruit of which ripens here; for the mountains which crown the lake serve as a shelter against the cold winds." The perpendicular height of the ten terraces is more than 200 feet above the level of the water of the lake, and they decrease proportionably in their circuit as they rise, till they reach the top of the hill, where they end in an oblong area paved with fine stone, in the centre of which is the unicorn, and which is surrounded by a balustrade. From this area a fine prospect of the lake and the surrounding mountains is obtained.