DISTTJBBANCES OP THE SEA-LEVEL. 21 



ever to re-establish an equality of surface in all parts where an ac- 

 cidental disturbance has occurred. 



Kevertheless, the diversity of climates, of wmds, and of currents, 

 is such, that certain seas, separated from one another by a narrow 

 sthmu;, pre.,ent permanently unequal levels. Thus --ral German 

 en-riueers believe that they have established the fact that the Baltic 

 Sea into which a great number of considerable rivers discharge them- 

 Ses is on an "average some inches higher (?) than the ^orth 

 Sea * In the same manner the Atlantic, whose waters spread out on 

 one side into the North Sea, and on the other into the Mediterranean, 

 would have a mean level scarcely higher than that of the two basms 

 which it supplies; while the Black Sea and the G« f of Venice, 

 receiving, like the Baltic, several large rivers would, like the latter 

 be propo;tionably elevated. On the two sides of t^f I^'^™- f 

 Suez the waters are also found at slightly unequal heights^ Accord- 

 in- to the engineer Bourdaloue, the mean level of the Red Sea at 

 Suez exceeds by 31* inches that of the Mediterranean near Port 

 Said; at low tides the two sheets of water are perceptibly of the 

 same level, while at high-water the sea is sometimes higher by d, 

 feet in the Bay of Suez than at the northern extremity ot the 

 maritime canal. A similar difference, too, occurs between the Bay 

 of Colon and the Gulf of Panama, and there also it is the mass ot 

 water in which the tides have the fullest swell, that is to say, the 

 Pacific Ocean, which has the highest level. But the measurements 

 made on the always unstable level of the sea are very delicate 

 operations, as one can so easily make a mistake at starting, through 

 the oscillations of the ebb and flow; and over spaces of many miles, 

 divided by various obstacles, it is very difficult to avoid shght errors. 

 At all events, it is certain that the surface of the sea, unceasmgly 

 traversed and perturbed by winds, currents, and tides, is not per- 

 fectly horizontal at any point of the globe. 



♦ Woltmann ;— Von Hoff, reraiidermc/eit der ErdoberJIScU, t. iii. p. 328. 



