Between Walker Pass, latitude 35° 40' north, altitude 5248 feet, and Tioga Pass, latitude 37° 35' north, altitude 9941 feet, a distance of 158 miles on a north and south line, there are no highways across the high, eastern front of the Sierra Nevada Mountains of California. This great barrier to travel on east and west lines is commonly referred to as the High Sierra. The greatest elevation on its crest line is Mount Whitney, 14,496 feet, the highest summit in the United States. From Mount Whitney, at latitude 36° 35′ north, the elevation of the. crest line declines southward rather regularly in 65 miles, on a north and south line, to the elevation of Walker Pass. North of Mount Whitney there is, however, only little change in elevation of the higher points in the 93 miles to Tioga Pass. Thus, Mount Sill, latitude 37° 6' north, has an . . .