254 Notes on Upper California. 



The syenite often contained albite. In some places, the crys- 

 tals of hornblende in the white rock, were two or three inches 

 long. One variety was a grayish rock thickly speckled with 

 small square or rectangular spots of albite, the grayish base con- 

 sisting of a mixture of albite and fine crystals of hornblende. 

 This and many of the other varieties were beautiful rocks for 

 architectural purposes. The syenite graduated into a variety 



consisting almost wholly of hornblende. 



The talcose rock was either slaty or compact, and much of it 

 had the characteristic soapy feel. An imperfect steatite or soap- 

 stone was met with, too hard and gritty for the ordinary purposes 

 of this material. The compact variety has a siliceous or flinty 

 appearance, though generally some dull greenish shade from the 

 presence of a little talc or hornblende. It breaks with sharp an- 

 gles and is usually much fissured. 



October 5. — We continued our rugged way down the valley, 

 up and down the hills that border it on the west, travelling over 

 rocky declivities often covered with sharp broken stone and in 

 many places barely accessible. The hills to the eastward were 

 still higher and more abrupt, varying according to our esti- 

 mate, from eight hundred to eighteen hundred feet. Destruction 

 river dashed noisily along its stony bed, confined much of the way 

 on both sides between hills several hundred feet high. We left 

 the granite after a while for hornblende rock and the talcose rock 

 formation, the last prevailing through the latter part of the day. 

 Often the two kinds of rock were closely associated or intermin- 

 gled as if parts of the same formation, the pearly talcose slate oc- 

 curring in the same ledge with hornblende slate. The talcose 

 varieties were often compact and broke into angular fragments. 

 The schistose structure when apparent, and the principal frac- 

 tures, were nearly vertical in dip. Occasionally the rock had the 

 color of serpentine, and a variegated appearance like verd-antique 

 marble ; then again it was pale copper-blue or light green, in color. 

 It passed also into a hypersthene rock, somewhat schistose, con- 

 taining pearly plates of hypersthene. At two places we observed 

 broad dikes of porphyritic basalt, with a corresponding change in 

 the soil. 



October 6. — Through the day, ascending and descending the 

 mountains that enclose the valley of Destruction river. It WW 

 not unfrequent that a pack-horse, upon a steep ascent, fell over 

 backward and rolled down hill with his load : yet there were no 

 serious accidents. The horse tried his legs again with better suc- 

 cess for his experience. At noon we climbed a steep ridge to a 

 height of 800 feet, and then began an immediate descent to a 

 still greater depth. The rock thus far (excepting some dikes ot 

 porphyritic basalt) had been talcose, and a dark blue-black argil- 

 lite with a talcose lustre ; the latter was thin fissile, and though 



