VOLCANOES. 
87 
seen both south and north of the line, and the volcano found as far south as the great bend of 
the Hawilhamook, together with the volcanoes and craters found on other lines of survey, both 
south and north, show that the volcanic vents are not distributed along an east and west line, 
but that they are probably found in long lines coincident with the trends of the principal chains 
of mountains. 
Age of the volcanoes .—It is probable that all these volcanoes are more recent than the Ter¬ 
tiary. We are aware that the cones and the lava of San Mateo and San Francisco overspread 
the strata of the plains, which are supposed to be synchronous in their origin with those on the 
east of the Anahuachian chain. That these are overspread with Tertiary deposites is extremely 
probable, although we are without any evidence presented by fossils. We have, however, seen 
that in many places the lava-streams have coursed down the valleys of the streams—the very 
rivers having been displaced by the molten flood. This shows the comparatively modern activity 
of some of these vents, and yet we are without any record or tradition of their action. 
I regret that it has not been possible to give the specimens of lava a full chemical examination, 
or to compare them with specimens from Europe. Some important and interesting observations 
upon them will be found in the letter from Baron Yon Humboldt, addressed to Captain Whip¬ 
ple, and published in Part I of his Report. 
