158 J. C. Branner — Geology of Fernando de Noronha. 



forms upon decomposition a deep red earth which gives name 

 to this part of the island — " Barro Vermelho," red mud. 



The Portao. — The extreme western portion of the island 

 lying west of the Portao Grande is known as the Sapato (the 

 shoe). This is one of the most interesting and impressive 

 places on Fernando. The waves have cut away the soft beds 



The Portao. 



of dark brown basaltic tuff which here form the greater part of 

 the strata of the island, until there remains little more than a 

 narrow neck of steep and rugged cliffs, some of them eighty 

 meters high, at whose breccia-covered foot breaks a ceaseless 

 and violent surf. At one place an opening or tunnel has pene- 

 trated the isthmus ; and this is the Portao Grande of the 

 inhabitants of Fernando — " the hole in the wall " of English 

 sailors. 



