United States Exploring Expedition. 17 



a manner so remarkable. On one of the high ridges of Ta- 

 hiti, (Society group,) about six thousand feet above the sea, 

 the summit edge is so sharp, and the sides of the mountain 

 so nearly vertical, that the adventurous traveller may sit astride 

 of it, and look down a precipice of a thousand feet on either 

 side. In no other way except by thus balancing and pushing 

 himself along is it possible, for about thirty feet, to advance 

 towards the summit before him yet a thousand feet higher 

 for the bushes which are growing on the crest elsewhere and 

 serve as a balustrade, are here wanting. The famous coral bed 

 on the mountains of Tahiti, was looked for without success. 



The Sandwich Islands contain basaltic rocks of all ages, from 

 the most recent volcanic to the most ancient in the Pacific, be- 

 sides coral rocks and elevated reefs ; and they are full of interest, 

 both as regards the structure and formation of igneous and lime- 

 stone rocks, and geological dynamics. The lofty precipices and 

 examples of shattered mountains before the eye. are astounding 

 to those who see only the little steeps, of a few hundred feet at 

 most, in the surface of our own country. There is evidence that 

 the island of Oahu is the shattered remnant of two lofty volcanic 

 mountains. A precipice on this island, upwards of twenty miles 

 long and from one to three thousand feet high, is apparently a 

 section of one of these volcanic mountains or domes, along which 

 it was rent in two, when the greater part was tumbled off and 

 submerged in the ocean. 



Oahu is fringed in part with a coral reef, twenty five feet out 

 of water ; and similar proofs of still greater elevation are met with 

 on the other islands. 



New Holland afforded the expedition a collection of coal plants 

 from the coal region ; the coal is bituminous and the beds are ex- 

 tensive. Large collections were also obtained of fossil shells and 

 corals, (about one hundred and eighty species in all,) from the 

 sandstone next below the coal. The geology of the coal region, 

 and of the overlying sandstone, and the fossiliferous sandstone 

 below, together with the trap dykes and beds, will prove highly 

 interesting. These are the only rocks observed. 



About one hundred species of fossils, including vertebras of ce- 

 tacea, and remains of four species of fish, crabs, echini and shells, 

 were collected from a clayey sandstone, near Astoria, on the Co- 

 lumbia. Various explorations were made in the interior of Ore- 

 gon, and on a jaunt overland to California. 



