44 



HYDROGRAPHY. 



In this neighborhood we encountered many tide rips, and found 

 the current, on trial, to set northeast by north three-quarters of a mile 

 per hour. 



Formerly it was deemed equally feasible as well as more advan- 

 tageous to pass to the eastward of the Cape de Verdes, to be enabled 

 to cross the equator on a more eastern meridian. Vessels now sel- 

 dom pursue this route, unless they have similar intentions with our- 

 selves, viz., to touch at St. Jago. 



Experience has proved that the best course for vessels to take that 

 are bound across the line, is to pass some distance to the westward of 

 San Antonio ; some, however, still prefer sighting this island, to ascer- 

 tain that the rates of their chronometers have not altered. 



Before leaving the Cape de Verdes, and as somewhat connected with 

 the interests of navigators, I may call attention to the remarkable 

 dry haze that frequently envelopes these islands, which renders all 

 objects indistinct, and at times entirely obscures the horizon, so as to 

 make it impossible to get observations with accuracy. Our observa- 

 tions place the fort at Porto Praya in latitude 14° 53' 45" north, 

 longitude 23° 30' 55" west. 



The supplies for ships at Porto Praya are not to be depended upon, 

 if required in a short time ; indeed, they are, at times, very difficult 

 to be had, the cultivation of late years having been much neglected, 

 in consequence of the few vessels visiting it, and the small demand in 

 comparison to what it was formerly. 



The magnetic variations decreased with regularity from Madeira to 

 the Cape de Verdes, viz., from 24° to 17° westwardly. 



FROM THE CAPE DE VERDES TO RIO DE JANEIRO. 



From October 8th to November 20th, 1838. 



On leaving Porto Praya, my intention was to pass over the position 

 of several shoals, which were embraced in my orders, and which lie 

 on the route of ships in the part of the ocean we were to traverse. I 

 was, therefore, not particularly anxious to cross the equator on any 

 particular meridian, but to be governed more by the opportunities I 

 might have of making our search as effectual as possible, without 

 losing too much time. 



We lost the northeast trade winds the day after we left Porto 



