` Where first observed, the conglomerate was composed of small, thoroughly-rounded pebbles; 
4 GEOLOGY. 
the ground looks rich and fertile. It is extensively cultivated, and fields were seen enclosed by 
the well known Virginia or “ crook fence." A steam saw-mill was in operation making boards 
from the pine logs. We remained at the anchorage only thirty minutes, long enough to 
land the mail in a small boat. 
Golden Gate, July 1.—Reached the headlands of the harbor of San Francisco early this *morn- 
ing. The fog was so dense that the shore was invisible until we were close upon it. A long 
and wide beach of white sand, which appeared to extend far inland, was passed before we 
entered the channel leading to the bay. Numerous small rocky islets fringe the headlands and 
make a dangerous surf. These islands were partly covered with sea-birds and the huge seals 
called sea-lions, Phoca (Otaria) jubata. The rocks are probably sandstone, but the fog was so 
dense about the top of the hills that the sky outline could not be observed. The shores are pre- 
cipitous ; vertical cliffs of rocks being exposed and apparently the result of the undermining 
action of the waves. 
San Francisco is built on the inner or eastern shore of the peninsula and at the foot of several 
hills of a brownish sandstone, partly covered with a thick soil, and in other places by sand. 
Towards the Mission the sand-hills are an important feature of the place, being high and steep, 
and covered in most places by a low growth of vegetation, principally shrubs and evergreen 
and dwarf oaks. Many of the buildings are constructed of a hewn sandstone, of a light-drab 
color, brought from Benicia, and of a beautiful light-colored granite brought from China. The 
fragments of the sandstone from Telegraph hill, near North Point, are so much stained and 
rusted by partial decomposition, and break up into such angular pieces, that they resemble 
trappean rock which has been exposed to the weather. 
SAN FRANCISCO TO THE SAN JOAQUIN RIVER. 
Benicia, July 8.—In passing up the bay of San Francisco by steamer to Benicia, many out- 
crops of stratified rocks are visible along the shores. Several small islands are also seen, one 
of them very red, being composed of a ferruginous rock, probably sandstone; and another quite 
white, it being covered with birds, which leave a layer of guano as white as lime. In the face 
of a bluff, not far from Benicia, the edges of stratified rocks were seen, the dip being about 
forty-seven degrees, and towards the southwest. 
At Benicia the hills are high and beautifully rounded, the surface being smooth and devoid 
of trees or shrubs. At this season, the wild oat, which covers the surface, is golden yellow ; 
but here and there the long dry straw has been set on fire, and broad acres are burned off, 
leaving a black, charred waste. ‘The general character of the surface of these hills is well shown 
by View II. 
Near the old barracks, there is an outcrop of coarse-grained sandstone and conglomerate. 
This being harder than the strata of finer materials, has resisted degradation, and now forms 
the apex of the hills.at many places. Its trend at one point appeared to be north 109 er 
0 
nearly uniform size, and not larger than peas or beans. Much larger pebbles were found at 
other points, and were probably derived from an adjoining stratum. The great bed of con- 
glomerate extends down io the water, and forms the headland, called Navy Point. At this 
place there is a fine exposure of sandstone, strata, and shales, all conformable with the con- 
glomerate. A good section was obtained. The strata are partly decomposed and rusted by 
