2 GEOLOGICAL REPORT—THIRTY-FIFTH PARALLEL. 
westward, and the ascent of the numerous ranges and ridges forming the eastern rim of the 
Great Basin is commenced. Crossing these at the end of the Mojave river, the Great Basin is 
traversed along the valley of that stream and the Mormon trail to the Cajon Pass in the trans- 
verse mountain chain, the southern prolongation of the Sierra Nevada, for which I have 
proposed the name Bernardino Sierra. After this chain is crossed, the broad and gentle slope 
extending to the Pacific is reached, and the line passes the rich and fertile valley of Bernardino, 
and crosses the valleys of numerous beautiful streams to the city of Los Angeles, and from. 
thence to San Pedro, its seaport, seventy miles distant. 
The country thus traversed presents a great variety of surface and diversity of scenery. It 
includes lofty mountain chains, isolated lava-covered peaks, broad elevated table-lands, fertile 
river-valleys, treeless wastes, deserts, and broad alluvial plains, burdened with vegetation. 
The leading features of the relief of the surface are well presented by the barometric profile, 
which is the result of numerous and careful observations. This profile, however, being con- 
structed to show the grades between each camp, for the whole line, and therefore being on a 
somewhat circuitous base, and passing over the mountain ranges at their lowest parts, does not 
give to us the most correct view of the relief of the surface along a direct line—a line trans- 
verse to the axes of the principal elevations and depressions. It is a railroad and not a physi- 
cal profile. This difference has been regarded in the construction of the geological section, and 
the modifications which have been made will be explained when the section is described. For 
the present purpose, also, this difference has been noted, and the succeeding remarks on the 
physical geography are the result not only of examinations of the profile, but also of the 
topography, as shown on the map, and, in part, known from personal observation. 
I propose to first present the most important particulars concerning the mountain ranges, 
then to consider the plains or plateaux and the mountain slopes, the rivers and their valleys, 
and lastly some general observations on the combination of these leading features. 
The parallel of 35? between the Mississippi and the Pacific ocean is intersected by five 
prominent mountain chains or combinations of ranges, producing distinctly defined swells of 
the surface, and these are separated by broad and equally well defined valleys or plains. The 
line surveyed may be said to cross six chains ; the sixth, that fronting the Pacific, being nearly 
coincident in its direction with the parallel of 35?. "These chains may be enumerated in their 
succession from east to west, as follows: First, the Sandia mountains, Gold mountains, and 
Santa Fé mountains, bordering the valley of the Rio Grande on the east ; second, the Sierra 
Madre, sometimes called Sierra de Zuñi; third, the Aztec and Aquarius mountains ; fourth, 
the Cerbat mountains ; and fifth, the Pai-Ute ranges, or the ranges forming the eastern rim of the 
Great Basin, and separating it from the Colorado river. The last or sixth chain is the Bernar- 
dino Sierra, of California. In addition to these lines of elevation we may add the prominent 
elevation produced by the voleano of San Francisco, and which, although the line of survey 
was at its southern base, produces a very striking modification of the profile, as if it traversed 
a mountain chain. This, however, so far as the topographical indications show, is not the case, 
and the elevation of that country shown in the profile is probably local, and not found several 
miles further to the north. 
In addition to the lines of elevation enumerated above, there is one which does not appear in 
the profile, and which being contiguous to the line of survey, demands attention in this place. 
This is the Sierra de Mogoyon, which was seen beyond the Sierra Madre, at the south of 
the line of exploration, and which appeared to extend for a long distance nearly parallel to it. 
Sandia and Santa Fé Ranges.—These mountains form the eastern border of the valley of 
the Rio Grande, and are the first abrupt elevations met with on passing west from the Mississippi 
river along the 35th parallel. At this point they do not present one continuous ridge, but are 
much broken and are traversed by several low and open passes. The line surveyed extends 
through one of these, and the highest point reached was 6,624 feet above the level of the sea. 
These mountains area part of the southern prolongation of the Park mountains. Further 
