18 GEOLOGY. 
About eight miles from camp, in an easterly direction, I observed a peculiar porphyritic 
syenite that apparently underlaid the granite, and gave indications of being more recent in age, 
The exposure was so slight at this place that sufficient evidence on this point could not be 
obtained. 
Many.miners were at work at different points along the stream washing the gold out of the 
sand with a common cradle. It was stated that they could not make much more than their 
expenses ; nearly all the gold they obtained being traded at a neighboring store for provisions 
and goods. The gold is in fine scales; higher up it is much more coarse, and in large grains 
and masses. ۱ 
Leaving the stream, and travelling south towards the San Joaquin, I passed over a succession 
of granite ridges for fifteen miles, following Indian trails. These. ridges were thinly covered 
with oak and pine trees. The narrow valleys or gulches between them were entirely dry, but 
are evidently traversed by brooks during the rainy season. Gneissoidal granite, passing into 
& coarse mica slate, traversed by quartz veins, was passed just before reaching the San Joaquin 
river, about two miles below Fort Miller. 
During this day's ride numerous table-hills or mesas were seen on the right, but several 
miles distant, and apparently out upon the plain. They were also observed by the main party 
in their transit from the Fresno to the San Joaquin along the plain, and a sketch was made by 
Mr. Koppel. é 
The mesas appeared to extend far up towards the high mountains, which, towering In the 
distance, were white with snow. The cap-rock of the hills was remarkably even and flat, and 
subsequent exploration showed that it was composed of hard, basaltic lava overlying soft strata, 
probably Tertiary 
AS E 
