240 MULE-HUNTING EXPEDITION. 
from one of the springs so as to fill a small room 
with steam. 
It is one of the most singular and interesting 
places I have ever visited. ~ There can be no 
doubt that the springs rise from the crater of 
an extinct volcano, and that there is some active 
volcanic action still gomg on in the depths 
below. Incrustations of various salts and sul- 
-phur covered the edges of the pools and rocks 
over which the water runs. The water they 
drink has to be brought from a spring the other 
side of the encircling hills. 
Although at this place I observed more direct 
evidence of some great internal fire or subter- 
ranean laboratory, in which Nature is ever trans- 
forming the elemental forms of crude matter into 
available materials for the supply of organic life; 
still throughout Oregon and California I have 
constantly come across similar sulphurous and 
saline eruptions, particularly soda-water springs, 
where the water rises through the earth, tho- 
roughly impregnated with carbonic-acid gas. 
At Nappa, not far from San Francisco, native 
soda-water is collected and bottled at the springs 
for the supply of the San Francisco market. 
Olympian nectar was never more grateful to the 
