HYDROGRAPHY. 3 



It is difficult from the absence of soundings between the southernmost 

 lines of the '"Albatross" and those of the '•Challenger" in the latitude of 

 Valparaiso to fix any limit to the Buchan Basin. For this reason I have 

 merely kept the legend without attempting to define its boundaries. 



The line from Callao to Easter Island (PI. 10, fig. 1), passes through Milne- 

 Edwards Deep, which is separated from the southern part of Bowers Basin 

 having a depth of over 2700 fathoms, by a ridge of about 2500 fathoms. 



The slope of that line rises very gradually from 2400 fathoms to the 

 2000-fathom line, forming the eastern flank of the plateau enclosing Sala y 

 Gomez and Easter Island. The latter, the larger island, rises more suddenly 

 from a much smaller plateau than the one of which the small rocky islet of 

 Sala y Gomez is the visible area (PL 1), the 1500-fathom line extending 

 nearly half-way from Sala y Gomez to Easter Island and within a short 

 distance of Easter Island connecting Sala y Gomez and Easter Island. On the 

 ridge we found 1142 fathoms near Sala y Gomez, and 1696 fathoms half-way 

 between that point and Easter Island. The ridge rises rapidly from about 

 2000 fathoms, the general oceanic depth within about 100 miles, to over 

 1100 fathoms within a comparatively short distance from both Sala y 

 Gomez and Easter Island. 



The plateau connecting Sala y Gomez and Easter Island forms a marked 

 spur on the southeast point of the Albatross Plateau (PI. 1). 



The two lines centering at Easter Island (Pis. 4, 10, fig. 1), developed the 

 eastern edge of the Albatross Plateau (Pis. 5, 6, fig. 1, 9, 11, 12), indicated on 

 the "Challenger" bathymetrical charts, on the strength of a few soundings 

 reaching from Callao in a northwesterly direction and of a couple of sound- 

 ings on the 20th degree of latitude. It is surprising that with the few 

 soundings known at the time the " Challenger " charts were published so 

 accurate a sketch of the Albatross Plateau should have been made, and still 

 more interesting that the plateau should have been called the " Albatrpss " 

 Plateau, and be developed by the " Albatross " nearly thirty years later. 



The " Albatross " Plateau is the most interesting bathymetrical feature 

 of the Eastern Pacific (Pis. 5, 6, fig. 1, 9, 11, 12). It is a triangular area 

 (PI. 1), indicated by the 2000-fathom line pointing towards the Galapagos, 

 with a base starting from Easter Island almost reaching Manga Reva. 



According to the "Challenger" bathymetrical chart (PI. IB), the Juan 

 Fernandez Plateau connects with the Albatross Plateau and forms the 

 .southern limit separating Buchan Basin from Barker Basin south of the Juan 



