140 GEOGRAPHY. 



Caspian Sea. 



The surface of the Caspian Sea, is 334 feet (a 

 French author says 50 toises) beneath that of the 

 Black Sea, and its shores may perhaps be considered 

 the lowest country in the world. 



Lake Superior. 



Lake Superior is 617 feet above the level of the 

 Atlantic, and 52 feet above Lake Erie. Extreme 

 length, 541 miles ; extreme breadth, 140 miles. 



Tides. 



In the open sea, the tides are at their height three 

 hours after the moon has passed the meridian of the 

 place, and of the meridian opposite. They are 

 smallest towards the poles, and greatest towards the 

 equator, where, however, they do not exceed two or 

 three feet in the great ocean. Their greatest elevation 

 takes place in the narrow seas, when the action of 

 the moon is aided by winds and currents, the position 

 of the coast, &c. The highest tides in Europe are 

 in the Gulf of St. Maloes, where the flood, driven 

 back by the coast of England, rises to the height of 

 seven or eight fathoms ; but at Annapolis, in the Bay 

 of Fundy, (where the bore also is tremendous,) the 

 water sometimes rises above 100 feet. Inland seas, 

 whose entrances face the west, have rarely any tides, 

 because the moon acts on all their parts at once, and 

 there are no lateral waters to flow in and produce a 

 local elevation. 



The regular period of flux and 'reflux is 12 hours 

 50J minutes, so that the tides return later and later 

 each day by 50 J minutes, which is the excess of a 

 lunar day over a solar one, since 28J lunar days are 

 nearly equal to 29J solar ones. 



