164 
GEOLOGY. 
composed of large and detached blocks heaped upon one another, and rising to the 
greatest height towards the middle of the island ; the whole has the appearance of an 
ancient volcanic production. — C. 
EASTER ISLAND 
Has its surface diversified by hills and valleys. Many of the hills have round and 
hollowed tops (the remains of extinct volcanos). The valleys are of gradual ascent, and 
covered with bare grey stones and a scanty verdure. The high and perpendicular shore 
of the eastern end is formed of distinct horizontal strata of volcanic rocks, resembling 
some parts of the Giant’s Causeway ; but I saw none that assume the regular columnar 
form. 
The rocks upon which we landed in Cook’s Bay were a hard vesicular lava of an ash 
grey colour, and the missiles discharged at us by the natives from behind these rocks 
were lava of different degrees of hardness, some so soft and decayed as to break with 
the fall. — C. 
PITCAIRN ISLAND. 
Rises bold, precipitous and irregular, out of the sea to the height of about 700 feet, 
with a circumference of nearly four miles. On the north side the slope is gradual, and 
indented with valleys. To the westward is a steep mountain ridge, excavated in some 
places into caverns, which afford shelter to the goats. This forms one end of the high 
and broken ridge, which extends round by the south to the eastern extremity of the 
island, where it terminates in the lofty cliff that looks down upon the north-east landing 
place called Bounty Bay. The ascent from the beach everywhere, except on the nor- 
thern side, is so steep as in many places to be almost impracticable. The whole of the 
island is of ancient volcanic formation, and in most places is composed of a conglome- 
rated tufa, so loose that it is easily converted into a dry gravelly soil, producing yams, 
taro, tee, yappe, sweet potatoes, &c. There is a reddish colouring over the greater part 
of the island, excepting the precipices which terminate each extremity of the high ridge. 
The western extremity is a black and easily disintegrated tufa, with imbedded masses of 
compact lava. The north-eastern end is a grey arenaceous tufa, varying in hardness, 
and has been unequally worn into grooves and projections, smoothed as if by art. The 
rocks near the sea in Bounty Bay, and along the northern shore, are chiefly formed of a 
porous lava inclosing crystals of felspar. 
The sea around the island is deep close to the shore. Pieces of recent coral are 
thrown upon the rocky beach. 
Specimens from Pitcairn Island. 
Vesicular lava, containing large crystals of glassy felspar; — Volcanic tufa, com- 
posed of small angular portions of porous and of compact lava, with a yellowish green 
earth imbedded, and traces of zeolites; — Basaltic lava, with imbedded olivine; — 
Obsidian. — C. 
