XX Physical and Geognostic Suggestions, 



commences at a considerable distance from the Capes of 

 St. Roqiie and St. Augustin. This bifurcation has always, 

 and with good reason, been ascribed to the protruding 

 convexity of the South American continent at these two 

 promontories. It would be an important step gained in 

 verifying the theory of currents, could the precise distance 

 be ascertained by chronometer. It is apparently like an 

 " actio in distans,^^ probably a phenomenon of what is known 

 as " packing." As the frigate, on leaving Rio de Janeiro is 

 to make for the Cape of Good Hope, the opportunity will 

 present, should she steer sufficiently southerly, for many 

 interesting observations with respect to the connecting cur- 

 rent W.N.W. and E.S.E. which encounters that from Mada- 

 gascar and Mozambique, close to the Cape, more especially 

 with regard to the temperature of the sea. 



If the frigate is intended to approach the small cluster of 

 islands of Fernando de Noronha, E. of Pernambuco (Lat. 

 3°, 50' S.), I would recommend to that excellent geognostic, 

 Dr. Hochstetter, the hornblendic phonolithe rock found there, 

 far from a volcanic crater, but with trachytic dykes and 

 basaltic amygdaloid. The flat little island of St. Paul 

 (Peiiedo de San Pedro), V N. Lat., singular to say, is not 

 volcanic at all, containing, like the Malouin or Falkland 

 Islands, slaty green-stone passing into serpentine. 



Should the frigate alter her course and cross the Equator 

 more to the eastward, without touching at Rio de Janeiro, 

 she might possibly fall in with the Marine Volcanic region, 



