GULF OF DARIEN. 



317 



and fseveval, with, springs of e-ood water, hav^e been occupied hj a few Indian 

 communities. 



Beyond tlie Muletas the cays are scattered in disorder along the coast, forming 

 an outer barrier reef as far as the Puerto Escocès. Farther on the sea becomes 

 quite free of these obstructions in the direction of the Gvdf of Darien (IJraba), 

 where, however, begins a fresh formation, that of the alluvial matter deposited by 

 the mouths of the Atrato. Here the sands and shore-line are continually shifting, 

 with the current, so that the marine charts should be revised every year. 



In the Gulf of Darien the same process of silting, but on a much larger scale, 

 is going on as in that of Smyrna in Asia Minor. The potent current of the 

 Atrato is continually impelling the alluvial banks in the direction of the South 



Fig. 142. — Gulf of San Blas. 

 Scale 1 : 600,000. 



79° West oP Grppnv-MrV, 





Olo 16 

 Feet. 



Depths. 



16 to 32 



Feet. 



32 Feet anl 

 upwards. 



12 Miles. 



American side, so that the southern part of the bay cannot fail, sooner or later, to 

 be cut off from the open sea. 



The contrast between the Atlantic and Pacific seaboards is primarily due to 

 the tides, which vary far more on one side than the other. At the mouth of the 

 Chagres river and in Colon Bay there is a mean rise of 15 inches, and of one foot 

 in Chiriqui Bay, but this difference between ebb and flow is not constant, being 

 greatly modified according to the force and direction of the winds. At times the 

 surface remains at the same level for days together ; but as a rule the two 

 diurnal tides neutralise each other so far as to produce only a single rise and a 

 single fall in the twenty-four hours. 



On the Pacific coast, on the contrary, ebb and flow follow the normal course. 



