The physical phenomena which certain lakes present, have always excited the astonishment of the multitude. Those of the _periodical lakes_ are the most common. In Europe these are nothing but pools, but between the tropics these pools sometimes cover spaces of several hundred leagues in length and breadth. Such are the famous lakes of Xarages and Paria, inscribed on maps of America, and expunged from them by turns; it is probable that Africa contains a great many of this description. The depth of lakes varies infinitely, and cannot form a subject of general physical geography. The popular opinion, however, that there are lakes without a bottom, is erroneous. Those which have been considered as such, owe this character solely to the existence of currents which carry along with them the lead attached to the sounding line. The waters of lakes, being derived from springs and rivers, partake of their different qualities. There are some lakes, whose waters are extremely limpid, such as the lake of Geneva, and that of Wetter in Sweden; in the latter, a farthing may be perceived at the bottom of the lake, at one hundred and twenty feet depth; but the lakes whose waters are motionless, saline, or bituminous, may be looked upon as equally unwholesome with those of marshes. COMPARATIVE VIEW OF THE MOST CELEBRATED LAKES. WESTERN HEMISPHERE. _Square _Surface._ miles._ Lake Superior 22,400 Lake Michigan 12,600 Lake Huron 15,800 Lake Erie 4,800 Lake Ontario 4,450 Great Slave Lake 12,000 Great Bear Lake 4,000 Winnepeg Lake 7,200 Lake Maracaibo 6,000 Athabasca Lake 3,200 Lake Titicaca 5,400 Lake St. George 340 Lake Champlain 350 Lake of the Woods 1,600 EASTERN HEMISPHERE. Lake Tchad, Africa 11,600 Lake Ladoga, Russia 5,200 Lake Onega, Russia 3,300 Wetter Lake, Sweden 945 Lake of Constance, Switzerland 456 Geneva Lake, Switzerland 400 Loch Lomond, Scotland 27 Windermere Lake, England 11 Killarney Lake, Ireland 14 Loch Leven, Scotland 6