Crawford.] 550 l^^V '5. 
fissures from which these various springs How, but it is evident 
from the composition of the waters that they flow from different 
directions through fissures that converge to this depression. This 
opinion is confirmed b}^ the following facts : (1) Between the 
subgroup charged with bicarbonates and the base of the cone 
Obraje, where large springs depositing travertine are found, is a 
depression from the floor of which bicarbonated waters bubble up 
in small quantities, which on i;ooling deposit travertine ; (2) 
Between another subgroup of springs, which are impregnated 
with iron in solution, and the cone Uval, where iron oxides are 
exposed abundantly, there is a deep depression from the floor of 
which waters that are nearly saturated with iron exude in small 
quantities. The sources of the springs from which halcite crys- 
talizes on cooling and those from which silicates are deposited on 
cooling were not satisfactorily discovered. These springs together 
foi-m a creek of hot water about 7 miles long, which flows west 
uito the tide- water estuary, Estera real. 
Mud springs. — 1. At the eastern termination of Cerro Vie jo, 
and at an altitude of 2,500 feet above the ocean, the apex of the 
volcanic cone Santa Maria is nearly encircled by a wide belt of 
mud springs. Their orifice is froin 8 inches to 4 feet in diameter, 
and they have built up around themselves walls of pyroxene mud 
from 1 to 3 feet high that have become semi-hardened. The 
boiling mud oscillates up and down, but seldom rises to the rim 
of its surrounding wall of mud. Tlie ground or space between 
these springs sustained, wherever tested, the weight of a man and 
horse, but sank perceptibly, returning after a few vibrations to its 
normal level when relieved of the pressure. Within a few feet 
of these springs, however, both above and below them, the Cerro 
is formed of inelastic lavas. All these mud springs appear to 
flow from a fissure of nearly circular form, over a hundred feet 
wide, and nearlj^ surrounding the ci-ater at the apex of the cone. 
2. At an elevation of about 4,400 feet on the northeast side of 
the cone ITval, near its apex, there are numerous mud springs 
similar in general features to those on Santa Maria above 
described, but the walls deposited by the waters overarch and 
nearly conceal the springs. The rise and fall of the hot mud in 
these springs is periodic and uniform, there being a complete 
oscillation every two hours. 
I 
