185 San Juan alt [altitude] 1800 Sections about 90 ft [feet] gravel mostly decayed but still well formed & entire but crumbling when exposed to all excepting the quartz & granite & a few of the more siliceous lavas. Very few heavy bowlders Planes of stratification clear but irregular, like those of deltas. Bed rock granite thouroughly decomposed more irregular on sides than bottom. Gold found mostly in lowest portions.
186 * Whether the ancient rivers were preglacial in age or interglacial does not yet appear Certainly they were prior in time to the cutting by gls [glaciers] of the present water courses The whole system of the present rivers as far as I have observed was eroded by gls [glaciers] subsequent to the period in wh [which] the ancient rivers lived -- the deposition of the gravel belts & the outpouring of the lavas wh [which] cap them --
Original journal dimensions: 9 x 14.5 cm.
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John Muir, journals, drawings, writings, travel, journaling, naturalist