MINES OF A.LUM. 113 



isthmus which, stretching from north to south, formerly 

 joined the peninsula of A.raya to the island of Margareta. 

 In that island a neck of very low land, three thousand 

 toises long, and less than two hundred toises broad, conceals 

 on the northern sides the two hilly groups, known by the 

 names of La Vega de San Juan, and the Macanap. The 

 Laguna Grande of Margareta has a very narrow opening to 

 the south, and small boats pass by portage over the neck of 

 land or northern dyke. Though the waters on these shores 

 seem at present to recede from the continent, it is neverthe- 

 less very probable, that in the lapse of ages, either by ay 

 earthquake or by a sudden rising of the ocean, the long 

 island of Margareta will be divided into two rocky islands of 

 a trapezoidal form. 



The limestone of the Barigon, which is a part of the great 

 formation of sandstone or calcareous breccia of Cumana, is 

 filled with fossil shells in as perfect preservation as those of 

 other tertiary limestones in Fran-ce and Italy. "We detached 

 some blocks, containing oysters eight inches in diameter, 

 pectens, venuses, and lithophyte polypi. I recommend to 

 naturalists better versed in the knowledge of fossils than I 

 then was, to examine with care this mountainous coast 

 (which is easy of access to European vessels), in their way 

 to Cumana, Guayra, or Cura9ao. It would be curious to 

 discover whether any of these shells, and these species of 

 petrified zoophytes, still inhabit the sea of the West Indies, 

 as M. Bonpland conjectured, and as is the case in the island 

 of Timor, and perhaps in Guadaloupe. 



We sailed on the 4th of November, at one o'clock in the 

 morning, in search of the mine of native alum. I took 

 with me the chronometer and my large Dollond telescope, 

 intending to observe at the Laguna Chica (Small Lake), east 

 of the village of Maniquarez, the immersion of the first 

 satellite of Jupiter ; this design, however, was not accom- 

 plished, contrary winds having prevented our arrival before 

 daylight. The spectacle of the phosphorescence of the 

 .11, and the sports of the porpoises which surrounded 

 our canoe, somewhat atoned for this disappointment. We 

 i passed those spots where springs of petroleum gush 

 from mica-slate at the bottom of the sea, and the smell of 

 is perceptible from a considerable distance. When it 



TUL HI. I 



