Some lakes have a double bottom, which rising and sinking alter nately changes the apparent depth of the lake; there is a lake of this kind at Jemtia in Sweden.
Some lakes are said to have no bottom ; but this is an impossibility : the fact is, that the sound does not reach the bottom, either for want of sufficient weight of lead or length of line, or else it is carried away by undercurrents.
In Poland there exists a lake said to render brown the skin of those who bathe in it. Certain mineral waters impregnated with sulphu retted hydrogen are well known to change from white to brown the skins of those persons who have been under a course of metallic medi cines, or who use metallic cosmetics, and some such circumstance may be the case with the lake in question.
Some lakes are intermittent : the most remarkable of this kind aro those of Cirknitz in Illyria, and Kauten in Prussia. They are sup posed to be occasioned by a play of natural siphons, upon the same principle as intermittent fountains.
The Lake of Geneva is subject to a subaqueous wind, called the Vaudaise, which, rising to the surface, produces an agitation of the water which is sometimes dangerous to the navigation of the lake. Near Boleslaw in Bohemia there is a lake of unknown depth, from the bottom of which there rise, in winter, such violent puffs of wind, that they are said to send up into the air masses of ice of several hundred pounds weight. The sudden escape of gases formed in the bowels of the earth, and perhaps the air forcibly driven out from caverns by the water rushing into and filling them up, may be among the causes of this remarkable phenomenon.
The Seiches are a phenomenon which has hitherto been observed only in the Lake of Geneva and some other of the Swiss and Italian lakes, though it is probably common to many others. It consists in an occasional undulation of the water, something like a tide wave, which rises occasionally to the height of 5 feet. Its cause in not exactly tenon, though it is most probably due to a local and temporary change f atmospheric prtesure. Watersrpouts are a phenomenon sometimes seen on lakes as on the sea ; they have been observed on the lakes of 'Uri& and Cream.
Certaio lakes seem to be placed in the immediate neighbourhood of centres or foci of electrical attraction; thug In the lake Huron there is a bay over which electrical clouds are perpetually hovering. It is rak rubol that DO person has ever traversed it without hearing thunder. Th. proximity of this lake to the American magnetic pole, that is, to the spot where the magnetic Intensity is greatest, not where the dip is greatest, may perhaps have some Influence in producing so remarkable a phenomenon.
Near Beja In Portugal there is a lake which is said to announce the approach of a storm by a tremendous rumbling. In Siberia also, near little river Oreilat, which flows into the Alaskan, there in according to Pallas, a lake called the Roaring Lake, from the dreadful noise it mikes, and which announces internal revolutions similar to that which occasioned the rupture of the dykes of the Lake Cousino1 in Douaria.
Some lakes have been observed to possess a petrifying or an incrust ing property. The latter is merely a deposition of carbonate of lime. This, being dissolved by an excess of acid In the waters of certain erring., is precipitated whenever the waters of these sources coming into the lakes are exposed to the air and lose their excess of acid.
There is an interesting phenomenon presented by the Lake of airich, called the flowering of the lake. When this takes place the surface of the water is seen covered with a yellow scum or froth, which upon examination is found to be a very minute vegetation.
There are various other phenomena presented by lakes, but the most singular of them all perhaps is the attractive force of the mud at the bottom of some lakes, which is such that boats can hardly make their way through the water. The Lake Rose and one or two more in Canada are of this kind. Mackenzie describes the fact in these words :—" At thlportage or carrying-place of Martres, on Rose Lake, the water is only three or four feet deep, and the bottom Is muddy. I have often plunged into it a pole twelve feet long, with as much ease as if I merely plunged it into the water. Nevertheless tbis mud has a sort of magical effect upon the boats, which is such that the paddles can with difficulty urge them on. This effect is not perceptible on the south aide of the lake, where the water is deep, but is more and more sensible as you approach the opposite shore. I have been assured that loaded boats have often been in danger of sinking, and could only be extricated by being towed by lighter boats. As for myself, I have never been in danger of foundering, but I have several times had great difficulty in pealing this spot with six stout rowers, whose utmost efforts could scarcely overcome the attraction of the mud. A similar phenomenon Is observed on the lake Saginega, whose bottom attracts the boats with such force that it is only with the greatest difficulty that a loaded boat can be made to advance; fortunately the spot is only about 400 yards over." Captain Back has confirmed the above by later observations.