GEOLOGY — SUISUN VALLEY. 19 



marshy. The sandstone hills are covered with wild oats and cultivated to their summits, hut 

 the trap ranges are rough, rugged, and valueless. 



SUISUN VALLEY. 



This valley is enclosed between two ranges of hills, of which those on the west are high and 

 rough, and formed of vesicular trap ; while those on the east are low, rounded, and apparently 

 composed of sandstone. 



Near where we crossed the eastern hills to Vacaville, a deposit of calcareous tufa was noticed, 

 similar to that at Goodhues. 



At Lagoon lake, and in that vicinity, the sandstones are fully exposed. I was able to dis- 

 cover no fossils, but the rock is identical in appearance with that at Benicia, and is doubtless 

 the same. 



