cdm inus 7 N 
GEOLOGY. 107 
The direct analysis gave : 
Silica : 50.93 
Protoxyd of iron and alumina 29.35 
Oxyd of calcium 10.33 
Oxyd of magnesium. 5.97 
Oxyd of sodium and potassium 3.42 
100.00 
The following is an analysis of a rock from the headwaters of Pitt river, by Mr. Gustavus 
Baumgarten, done in my laboratory and under my direction. The determination of silica gave 
57.65 per cent.; the rock isa mixture of 1 part normal trachytic, and 2.07 parts of normal 
pyroxenic rock: 
io argon aceord- loonigaditin "(ors 
cond for- by analysis 
Silica 57. 65 57. 65 
Late ty of iron and alumina 24, 97 27. 56 
calcium 8. 47 6. 53 
ad ir i magnesium 4.74 5.30 
Oxyd of sodium and potassium .............-.. ....| 4. 17 2. 91 
100. 00 100. 60 
These analyses hardly admit of any doubt as to the applicability of Bunsen’s law to the 
igneous rocks of the Sierra Nevada. It would seem that the hearth ofthe trachytic masses 
was lying north, and that of the normal pyroxenic masses more south; a greater number of 
rocks must, however, be analyzed before we can form a more reliable opinion on that point. 
In the Sierra we travelled for days over a red soil, which, according to the popular belief, is- 
gold-bearing. This seems, however, a mistake, produced by the resemblance of its color to 
that of the soil in the Sacramento valley. It comes from a disintegrated red volcanic rock, of 
which I found occasionally pieces of six inches in diameter. 
There is, however, an auriferous rock, the existence of which in California I find nowhere 
mentioned, which I found near the summit of one of the high peaks on the Upper Sacramento, - 
(Pitt river.) It isa red rock, with porphyritic structure, and of excessive hardness, bearing 
unmistakably the signs of gold. 
In the rugged Pitt river country, where Canoe creek émptioe into that river, and a short 
distance above the mouth of the creek, there is a kind of dam along the creek, made up of a 
white soil, which, a little remote from the creek, forms a regular stratum of considerable thick- 
ness. The rock around is a porphyritic trachyte, and no sedimentary rock of any kind could be 
detected. On examining this earth under the microscope, I found it to consist of the silicious 
coats of infusoria, and I therefore sent a specimen of it, together with a speeimen of infusorial 
earth, found in Hone} Lake valley, to Professor Bailey; at West Point, as the savan who is 
best amieiéio with American infusoria. According to him they are both made up of diato- 
maceous shells ; some of them are novel, and both are of fresh-water origin, containing many 
well known species still living all over our country. A fuller denti of the new species 
will be given by Professor Bailey. 
lam, sir, very mpi your obedient servant, 
JAMES SCHIEL, M. D., 
Surgeon and Geologist for Explorations for ohirat 
Pacific Railroad Route. 
Lieut. E. G. Becxwrrn, y 
3d U. S. Artillery, in charge of Explorations, 
