GENERAL DESCRIPTION OF THE COUNTRY. 41 



of the boundary^, wliere occurS; in all the ranges except the Coast Kange, the remarkable 

 depression in the continent^ or rather absence in the continuity of the ranges of mountains, 

 hereafter to be described. 



The Sierra Nevada, in latitude 33° N., branches; one great division unites with the Coast 

 Eange, forming the elevated promontory of Lower Californiaj and presenting, when figured 

 on the map, the appearance of the letter Y, (Tulare valley resting in the fork of the letter ;) 

 other branches or spurs are thrown off in a southeast direction,, crossing the Gila at the mouth, 

 and many miles above, and traversing the newly-acquired territory in the meridian of Santa 

 Cruz and Tucson. 



That range, as well as the Sierra Madre and the Rocky mountains, about the parallel of 32°, 

 lose their continuous character, and assume the forms that are graphically described in the western 

 country as lost mountains — ^that is to say, mountains which have no apparent connexion with 

 each other. They preserve, however, their general direction N. W, and S. E., showing that 

 the upheaving power which produced them was the same, but in diminished and irregular force. 

 They rise abruptly from the plateau, and disappear as suddenly, and, by winding around the 

 bases of these mountains^ it is possible to pass through the mountain system, in this region^ 

 near the parallel of 32°, almost on the level of the plateau ; so that if the sea were to rise 4,000 

 feet above its present level, the navigator could cross the continent near the 32d parallel of 

 latitude. He would been soundings of uniform depth, from the Gulf of California to the Pecos 

 river. He would see to the north and to the south prominent peaks and sierras, and at times 

 his passage would be narrow and intricate. At El Paso he would be within gun-shot of both 

 shores. 



I noticed this remarkable depression in the continent, in an exploration made by me in 1846, 

 and called to it the attention of Mr. Buchanan,^ then Secretary of State ; and it was upon this 

 information that he instructed our minister, then negotiating the treaty of Guadalupe Hidalgo, 

 not to take a line north of the 32d jjarallel of latitude, in the boundary between the United 

 States and Mexico. 



Passing to the south of this parallel, in about that of 31°, we find the plateau rising rapidly 

 to the table-lands of Mexico^ the ranges above described are no longer traceable, and the plateau 

 gives evidence of having been disturbed by tremendous plutoni<? forces, and the mountains 

 assume a loftier and more rugged and diversified appearance. As I have said before, the Sierra 

 Madre ran^ of mountains cannot be traced distinctly with our present information. 



mountains 



make it difficult 



Mexico 



the Sierra Madre. 



It may be a question whether the Eocky mountain range is not divided by the Rio Bravo • 

 and if so^ that which I have designated as the Sierra Madre of New Mexico will, in that case, 

 become a spur of the Rocky mountains. The geological formations to which I shall presently 

 refer, seem to favor this hypothesis. If this hypothesis be true, the Sierra Madre of New 

 Mexico and the Rocky mountain system are the same, and are only divided by the Rio Bravo. 

 But this is a question which does not affect the general topographical description of the 

 country, and may be disregarded here. What I have described refers more particularly to the 

 country west of the Rio Bravo. 



The Rocky mountain system, commencing in the north, beyond the source of this river, and 

 beyond the limits of the 49th degree of north latitude, is the distinguishing feature of the 



Vol. I 6 



