REMARKS ON THE MAP AND SECTION. 173 
sents 1,703 miles. Its entire length is 851.5 inches, and it is divided into twenty-three lines, 
each one, except the upper and lower, being 38.7 inches long. It was deemed best, even at the 
expense of marring the appearance of the section by crowding the lines, to place the whole 
representation on one sheet, in order to present a connected view from one end of the line to the 
other. 
In constructing the section, it was necessary to consider that one prominent object was to 
present a view of the geology directly along the line as it was surveyed. To represent on the 
section, however, the succession and character of the rocks along the trail exactly as they occur, 
would not permit the geological structure of the region to be exhibited. The detours to the 
north and south were chiefly parallel with the trend of the rocks, and consequently they could 
not be represented on a section in which structure was to be shown. It was of course important 
that the line of section should be transverse to the principal lines of structure. To securo this, 
and at the same time to present a fair view of the geology along the trail, the line indicated 
below was adopted, and wherever it does not coincide in direction with the trail, it is drawn 
upon the map. 
DIRECTION OF THE SECTION. 
From the Pacific ocean at San Pedro, the seaport of Los Angeles, by the trail to Camp 142. 
From Camp 142 in a straight line to Camp 139. 
From Camp 139 by the trail to Camp 133. 
From Camp 133 in a straight line to Camp 110. 
From Camp 110 by the trail to Camp 106. 
From Camp 106 in a straight line to Camp 97. 
From Camp 97 in a straight line to Camp 96. 
From Camp 96 in a straight line to Camp 94. 
From Camp 94 in a straight line to Camp 90. 
From Camp 90 in a straight line to Camp 81. 
From Camp 81 by the trail to Camp 12. 
From Camp 72 in a straight line to Camp 70. 
From Camp 90 by the trail to Camp 67. 
From Camp 67 in a straight line to Camp 65. 
From Camp 65 by the trail to Camp 63. 
From Camp 63 to the Rio Grande at Albuquerque. 
From Albuquerque in a straight line to Camp 58. 
From Camp 58 in a straight line to Tucumcari hill. 
From Tucumcari hill in a straight line to the eastern bluff of the Llano Estacado, south of 
Camp 42. 
From Camp 42 in a straight line to Camp 35. 
From Camp 35 in a straight line to Camp 19. 
From Camp 19 in a straight line to the eastern side of Delaware ridge, south of Camp 17. 
From Camp 17 by the trail to Fort Smith. 
From Fort Smith in a straight line to Little Rock. 
From Little Rock in a straight line to Helena, on the Mississippi river, about fifty miles south 
of Memphis. 
It would be better for geological purposes that the section should continue its westward di- 
rection from the valley of the Mojave at Soda lake, and not follow the trail in its bend to the 
south and passage of the Bernardino Sierra at the Cajon Pass. If it was extended directly west 
from the Mojave to the Sierra Nevada, at the Tejon Pass, or at the sources of Kern river, it 
would be transverse to the trend of the mountains, and present a view of the Great Basin and 
the metamorphic rocks of the Sierra, with the Miocene strata at their western base. The allu- 
vial and lacustrine deposites of the Tulares would also be shown, and the uplifted Tertiary 
