THE MEXICAN ElYEKS. 



43 



channel just north of San Bias Bay, opposite the Très Marias islets, which continue 

 north-westwards the normal trend of the coast, as indicated by the direction of the 

 shore-line south of Cape Corrientes. The alluvial matter washed down by the 

 Lerma has filled up a part of the space separating the mainland from this insular 

 group ; both northwards and southwards the land is encroaching seaward, and the 



Fig. 21. — COLOEADO ESTUAET. 

 Scale 1 : 850,U00. 



Ii5 



West oP GreenwicK Il4'40 



Depths. 



Oto 5 

 Fathoms. 



5 Fathoms 

 and upwards. 



Banks exposed 

 at low tides. 



=, 18 Miles. 



true coast at the foot of the hills is now washed by shallow lagoons which are pro- 

 tected by sandy strips from the open sea. 



North of the Rio Lerma no other copious rivers reach the Pacific within the 

 Mexican frontier ; even those which, like the Kio del Fuerte, the Rio Yaqui, and 

 the Sonora, have large catchment basins, roll down very little water. This is due 



