Chap. VIII. THE NORTH AMERICAN CONTINENT. 551 
such mistakes on the map of Europe, but have rectified 
the theories of geographers. Yet in their manner of 
representing other parts of the world, into which hypotheti- 
cal opinions must still enter largely, the effects of erroneous 
theories are not wholly removed ; and this, among others, is 
the case with North America, to the orological system of 
which country I here allude. Here a connexion of the 
great system of the Eocky Mountains with that of the 
Sierra Madre of the Western Mexico is still credited, to 
have the eastern and western slopes of the continent 
separated by a great mountain-chain coinciding with the 
watershed. But the actual nature of things contradicts 
this opinion. 
It would be far more correct to speak of a general con- 
nexion between all the mountain-chains and table-lands 
which occupy the whole western side of the New World, 
from Tierra del Fuego to the North Arctic Ocean. Con- 
ceived as a great system and contrasted with the extensive 
lowlands to the east of it, the western portion of the 
continent really forms a natural division, with subdivisions 
which, of course, are in some connexion with each other. 
But this fact is quite irrelevant to the question whether 
two secondary links in this system — the Bocky Mountains 
and the Sierra Madre — have any direct connexion, or 
whether, on correct principles, they can be regarded as 
orological equivalents in the construction of the whole. 
I shall endeavour to show that this is not the case. 
I. — The great chain of the Bocky Mountains is divided, 
near the sources of the Bio Grande, into two ranges, one 
of which follows the western, the other the eastern side of 
the river ; the latter as far as the latitude of Santa Fe. 
The reader who has followed me in my journey from 
Missouri to New Mexico, may perhaps remember that 
