36 United States Exploring Expedition. 



the expedition. This subject bears upon the distribution of 

 fossil animals, and the early history of our globe, and is excit- 

 ing much attention among those interested in geological inves- 

 tigations. 



The regions examined by the expedition have been highly 

 interesting in a geological point of view. The islands of the 

 Pacific east of New Caledonia are either basaltic or coralline. 

 A large number of the latter (as already stated) have been 

 examined, and much that is important has been brought to 

 light. The facts strongly confirm Darwin's theory with re- 

 gard to the formation of these islands, but lead to very difi^er- 

 ent conclusions respecting the areas of subsidence and eleva- 

 tion in the Pacific. Numerous facts bearing upon this subject 

 were collected. The basaltic islands are of various ages, from 

 the most recent volcanic to a very remote period, probably 

 as far back as the middle of the secondary era. The older 

 islands are remarkable for their singular topographical fea- 

 tures. There is scarcely any part of the world where such 

 profound gorges, and sharp and lofty peaks and ridges, are 

 thrown together in a manner so remarkable. On one of the 

 high ridges of Tahiti (Society group), about 6000 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 1000 feet 

 on either side. In no other way except by thus balancing and 

 pushing himself along is it possible, for about 30 feet, to ad- 

 vance towards the summit before him — yet 1000 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 Pa- 

 cific, besides coral rocks and elevated reefs ; and they are full 

 .of interest, both as regards the structure and formation of 

 igneous and limestone 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 



