Notes on Upper California. 259 



mer's sun. But the rains of the winter season, as with similar 

 soil in the Willammet. would probably develop great fertility. 



October 16. — To the south of our encampment there stood in 

 the flat prairie an isolated collection of summits, the highest of 

 which was about 1800 feet. It looked like a detached moun- 

 tain ridge, much broken into peaks, with long low slopes at 

 either extremity of the range, melting very gradually (at an 

 angle of 5°-8°) into the flat bottom land of the river. This is 





Sacramento Bute, bearing southeast-by-east. 



the Sacramento Bute, called also the Three Butes. It was 

 found to be an extinct volcano. The lower slopes are cut off in 

 most parts from the central mountainous portion by a flat valley, 

 three to four hundred yards wide ; and they face this valley, or 

 broad highway, with a mural front of one to three hundred feet. 

 In the figure, na is a profile view of the lower slope, the belt of the 

 Bute, which in many parts is a mile wide ; and at a is the preci- 

 pice bounding the interior valley. There are several openings to 

 the valley through the belt ; we entered by one of them on the 

 south, and after travelling seven miles emerged again on the 

 east, and at this eastern entrance encamped near a small pool of 

 standing water. 



■ The form of the Bute is nearly circular, and its diameter is about 

 eight miles ; it stands like an island in a vast prairie of millpond 

 smoothness. The inner valley is to a great extent at the same 

 level with the plains without, and during freshets, had evidently 

 been covered by water. 



The central peaks are steep and rugged, rising into bold crests 

 at top. The rock is porphyry, or trachytic porphyry. The 

 latter where first seen looked like a coarse syenitic gneiss. The 

 feldspar was in large translucent crystals, and through the base 

 small crystals of hornblende were disseminated. The usual colors 

 were gray, reddish or purplish, and white. Another variety was 

 laminated, and the laminae were thin and easily separable, at times 

 looking like porcelain. Some specimens were formed of alter- 

 ations of chalky and compact layers, and one block broken 

 °pen consisted of delicate stripes of white, light sepia brown, 

 ai *d a bright purple color. This laminated rock contained mica 



in hexagonal scales. 



The Bute was evidently a volcanic cone. It is probable that 

 the centre, at some period in its history, subsided, leaving only the 

 lower part of the slopes entire. As rocks and fragments from 

 ejections are not found over the prairie around, it was extinct be- 

 fore the present river flats were formed : and the overflow of the 

 river has since filled up and levelled off the surrounding country, 





