ON ITS EXTERIOR. VOLCANOES. 389 



by the United States government to seek for the best 

 route from the plains of the Mississippi to the shores of 

 the Pacific ; the expedition was also well prepared in 

 scientific respects, and all parts of natural history have 

 benefited by it. In the now explored terra incognita 

 of this interval, great strips of country, very near to 

 the Eocky Mountains on their eastern side, and extending 

 to a considerable distance from their western declivities, 

 have been found covered by the products of either 

 extinct or still active volcanoes. We may thus see that, 

 beginning from New Zealand, and proceeding first for a 

 considerable distance in a north-west direction we can 

 pass through New Gruinea, the Sunda islands, the 

 Philippines, and the east of Asia, and ascending to the 

 Aleutian islands, can redescend to the. southward 

 through the north-western part of America, Mexico, 

 Central and South America, to the extremity of Chili ; 

 thus making the entire circuit of the Pacific Ocean, and 

 finding it surrounded, throughout a length of 26,400 

 geographical miles, by a series of recognisable monu- 

 ments of volcanic activity. Such a general cosmical 

 view could not have been gained, and based on adequate 

 grounds, without entering into particulars of exact geo- 

 graphical direction and improved classification. 



Of the circumference of the great sea-basin here spoken 

 of, (or, inasmuch as there is but one throughout-com- 

 municating body of oceanic waters upon the earth, we 

 ought rather to say ( 533 ), of the circumference of the 

 largest of those portions of the ocean which form as it 

 were bays or gulfs between continents,) there still re- 

 main to be described the regions which extend from 

 the Eio Grila to Norton's and Kotzebue's Sounds. Analo- 



