CHAPTER L 
ISTHMUS OF DAHIEN TO SAN FRANCISCO-SAN FRANCISCO TO THE 
SAN JOAQUIN RIVER. 
Aspinwall on alluvial ground.—Fossils.—Tertiary fossils at gatun.—Argillaceous sandstone at barbacoas.—Chagres 
river.—Drift near gorgona.—Boulders and river-drift of igneous rocks at gorgona and cruces.—Cruces to panama.— 
Summit-ridges of the mountains, probably of compact greenstone.—Panama.—Strata of red sandstone.—Lignite.— 
Panama to san Francisco.—Basaltic islands.—Gulf of California—Mountains of the peninsula.—San diego.—Hills of 
modern strata.—Islands of santa Barbara channel.—Arched rock, anacapa.—Point conception.—Change of temperature 
AT CAPE CONCEPTION.—BlTUMEN.—POINT PINOS, MONTEREY.-—GRANITE -—GOLDEN GATE, SAN FRANCISCO SAND-BEACH.—SANDSTONE 
AND SAND HILLS.—SAN FRANCISCO TO BENICIA.—SANDSTONE STRATA.-—ROUNDED HILLS.—STRATUM OF CONGLOMERATE.—MARTINEZ — 
Mount diablo and diablo valley.—Sandstone and conglomerate.—Diallage rock from mount diablo.—Cracks in the soil.— 
Livermore’s valley.—Livermore’s pass.—Strata of sandstone and conglomerate—Outliers of conglomerate.—Effect of 
THE FIRES ON THE WILD OAT.-ELKHORN.-PLAIN OF THE SAN JOAQUIN.-Sloughs AND MARSHES OF THE RIVER. 
June 6, 1853.—Left New York for Aspinwall in the steamer Georgia,, and arrived on the 
morning of the 15th. The highlands of Porto Bello were seen on the left as we entered the 
hay, and on the right several high peaks loomed up in the distance, their deep blue color con¬ 
trasting finely with the luxuriant tropical verdure of the shores. Aspinwall is built on marshy, 
alluvial ground ; the margin of a tropical swamp. Wharves have, however, been built beyond 
the water line, and the intervening space was being filled in with earth brought down on the 
railroad from a place called Monkey Hill, generally known on the Isthmus as the burial ground 
for thousands who have died of the malarious fever contracted during the construction of the 
road. The earth is clayey, without much sand, and is strongly colored by oxide of iron and 
black films—-apparently, oxide of manganese. It is filled with casts of fossil shells; all marine. 
Bivalves were most numerous, and among them Pectens and Tellina were recognized. Other 
casts were probably of the genus Turritella; a tertiary or post-tertiary age is thus indicated 
for the formation from which the clay is obtained. 
Aspinwall to Barhacoas, June 16.—We proceeded from Aspinwall to Barbacoas by the rail¬ 
road ; the latter place is on Chagres river, and the present terminus of the road, the bridge not 
being complete. At Gatun, or Monkey Hill?, where we stopped for a few moments, I obtained 
several fossil shells from the embankment at the side of the road. They are very numerous, 
and well preserved in a greenish sandy clay, which is very soft, and apparently of quite recent 
formation. For want of time, only three species were procured. These have since been ex¬ 
amined and described by Mr. T. A. Conrad, and are new species of the genera Gratelupia, Mere- 
trix, and Tellina. —(See Appendix, Article II.) 
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