388 REACTION OF THE INTERIOR OF THE EARTH 



from sea to sea;, no two successive members have the 

 same mineralogical composition, a circumstance very 

 deserving of attention. 



North-western America 

 (North of the parallel of the Rio Gila). 



In the section which treated of the volcanic activity 

 of the East- Asiatic islands ( 332 ), particular importance 

 was attached to the bow-shaped curvature of the fissure, 

 of elevation from which the Aleutian islands have risen, 

 and which manifests an immediate connection between 

 the Asiatic and American continents, i. e. between the 

 two volcanic peninsulas Kamtschatka and Aliaska 

 (Alashka). We may call this the northern boundary of 

 a great bay of the Pacific Ocean, which, from a breadth 

 of 150 of longitude which it occupies at the equator, 

 diminishes to 3 7 of longitude between the points of the 

 two above-named peninsulas. On the American conti- 

 nent, near the sea, a number of more or less active volca- 

 noes have been known to mariners for the last seventy 

 or eighty years; but this group has been hitherto 

 regarded as isolated, unconnected either with the vol- 

 canic series of tropical Mexico, or with the volcanoes 

 supposed to exist in the peninsula of California. Now, 

 when a series of extinct trachytic cones are regarded as 

 intermediate links, an insight into their important geo- 

 logical connection has been gained by the filling up of 

 what was previously a gap, extending over more than 

 28 of latitude > between Durango and the new Wash- 

 ington territory north of West Oregon. This important 

 step in physical geography is due to the expedition sent 



