GEOLOGY VACAVILLE TO CHICO CREEK. 23 



grass, but everywhere sustaining a growth of green vegetation, except where covered with the 

 ripening wheat. A great breadth of surface was occupied by this crop, which the farmers told 

 me generally produced from 35 to 40 bushels to the acre. The drought of the present season 

 would reduce the yield to 25 to 30 bushels. 



The banks of the Sacramento, at Knight s Landing and at Fremont, where we crossed it, are 

 composed of fine alluvial earth, generally about 30 feet above the water-level at that time. A 

 belt of timber lines either side ; that near the water being willow, poplar, and sycamore, bound 

 together by grape vines ; further back the long-acorned oak, which, when the trees are crowded, 

 assumes the form of the white oak of the forests of the eastern States. 



No terraces are visible in the immediate vicinity of the Sacramento. Like those of Cache 

 creek, its banks have been formed by the stream when at nearly its present level, and belong 

 entirely to the present era. 



The water of Feather river, at the junction with the Sacramento, is so highly charged with 

 sediment, derived from the gold diggings on its tributaries, that it is rendered quite opaque, 

 and has a color as decided as that of the rivulets in the streets of our towns during a thunder- . 

 shower. 



The country bordering Feather river to Marysville presents no new geological features. No 

 rock is seen in place, and the banks of the stream are like those of the Sacramento, composed 

 of fine loamy earth, with very few pebbles as large as walnuts. The soil is excellent, and 

 melons and various crops are growing with considerable luxuriance. 



The red color of Feather river, so noticeable at its junction with the Sacramento, is for the 

 most part, derived from the Yuba, which, at Marysville, where they unite, has deposited such 

 quantities of sediment as to render its navigation impossible at a point considerably below 

 where boats could formerly run. 



The floods of the Yuba, which have occasioned so great destruction of property at Marysville, 

 have left piles of drift-wood forty feet above its bed. 



The want of building stone is severely felt in this vicinity. The houses in the town, since 

 the fires have swept away relays of wooden structures, have been all built of brick, and the 

 wharf at the steamboat landing is built of bags of sand. 



From Marysville, up the feather river, to Hamilton, we found no rock in place, and no trans 

 ported masses of any considerable size. The soil is generally a fine sandy loam near the river, 

 evidently fertile, and supporting a dense growth of vegetation; while the plains back from the 

 streams are frequently gravelly, and less productive, bearing a thin crop of coarse grasses, and 

 scattering trees of the two species of oak which have been mentioned, with occasional clumps 

 of manzanita. 



The gravel and rolled stones in the beds of the streams are generally composed of some form 

 of trappean rock, usually trap, porphyry, trachyte, &c., more rarely of quartz. These are, 

 probably, principally derived from the Sierra Nevada, but in part also from Slitter s buttes, 

 which are but about 10 miles distant from the road which we followed. 



These mountains have been distinctly visible since leaving Cache creek ; first as a single 

 peak, subsequently showing two others. They form, however, but a single mountain mass, 

 and should be denominated by a common name. From specimens brought from there, as well 

 as from the description given of them by Professor Dana, (Geol. Expl. Exped.,) we learn that 

 they are of volcanic origin, and not of recent date. 



They now rise like islands in the plain on which they stand, the highest point having an 

 altitude of about 1,800 feet above its general level. The alluvial deposits of the valley, which 



