132 
VOYAGE TO THE 
they may procure a supply of good water, than which nothing is more 
important to the navigation of these seas ; as that indispensable article 
is not found to exist in a pure state anywhere between Otaheite and 
the coast of Chili, a distance of 4000 miles, Pitcairn Island excepted, 
where the diiSculty of getting it olf has already been mentioned. It is 
also presumed, that the position of the islands having been ascertained, 
the peaks of Mount Dufl^ which are high and distinguishable at a great 
distance, will serve as a guide to the labyrinth of coral islands which 
the navigator, after passing this groupe, has to thread on his way to the 
westward, 
d his groupe was discovered by the ship Duff, on a missionary voyage, 
in 17975 and named by Mr. Wilson, her commander, after Admiral Lord 
Gambler. It consists of five large islands and several small ones, all 
situated in a lagoon formed by a reef of coral. The largest is about 
SIX mdes in length, and rises into two peaks, elevated 1248 feet above 
the level of the sea. These peaks, which were called after the Duff, 
are in the form of wedges, very conspicuous at a distance, and may be 
seen fourteen or fifteen leagues. All the islands are steep and rugged, 
particularly Marsh Island, which at a distance resembles a ship. The 
external forrn of these islands at once conveys an impression of their 
volcanic origin ; and, on examination, they all appeared to have been 
subjected to the action of great heat. 
“ The general basis of the rocks is a porous basaltic lava, in one 
place passing into a tuffacious slate ; in another, into the solid and 
angular column of compact basalt, containing the imbedded minerals 
which characterise this formation, and bearing a close resemblance in 
this particular to the basaltic formation of the county of Antrim in 
Ireland. There is, however, less of the basalt and more of the porous. 
The zealites, soapstone, chalcedony, olivine, and calcareous spar, are 
formed in, and connect the relationship of these distant formations ; 
whilst the different-coloured jaspers are peculiar to these islands. There 
is also another obvious distinctive feature produced by the numerous 
dykes of a formation differing in composition and texture, and marked by 
a defined line. They are generally more prominent than the common 
rock; traversing a great many, if not all the islands, in a direction nearly 
