104 



PORTO RICO 



citadels of San Juan are built upon a hill of this character, others 

 of which rise to the east and west of the city as far as Rio Grande 

 and toward Arecibo. They probably do not exceed 500 feet in 

 height at their interior side toward the mountains, but exact 

 measurements were not made. 



On the southwest end of the island there are two parallel rows 

 of hills separated from each other and the interior mountains by 

 long and fertile valleys. The interior chain, which extends from 

 north Cabo Rojo to within three miles of Yauco, passing west of 

 San German, is of a peculiar type not seen elsewhere upon the 



COAST HILLS NEAR CABO ROJO 



island. It is a single chain of high rounded wooded hills of 

 the type called knobs in this country and cerros by the Spaniards, 

 which owe their configuration to a thick cap stratum of hard 

 mountain limestone of Cretaceous age, the lower portion being 

 composed of the softer tuffs and decomposing rocks of the in- 

 terior mountains. Where this cap has been removed erosion 

 has widened the valleys into great elongated plains or vegas. 

 From the southwest cape of Porto Rico to within three or four 

 miles of Ponce, except where occasionally broken by playas, 

 coast hills are finely developed along the shore. These hills, 

 like those of the northwest coast, may be termed a dissected 



