150 TRANSACTIONS OF THE [FEB. 19, 
feet and climb over a hill to the trail, down which we can make 
our way by an equal use of hands and feet. 
Halfway down there is a break in the narrow ridge of rock, 
whose vertical side is one wall of the amphitheatre, and from 
this narrow opening, called La Ventana, or window, the first 
view of the falls is obtained during the descent. 
This is, perhaps, the most striking view of all; for the height 
of the fall, over 400 feet above and the depth of over 400 feet to 
the pool below, are brought in close comparison. The fall is 
hidden from sight as the trail winds down the debris at the foot 
of the cliffs. When at the bottom it is still a work of some difli- 
culty to make one’s way around the huge boulders to the pool, 
for what appeared from above to be heaps of gravel now proves 
to be masses of large boulders difficult to pass. There are large 
accumulations of rock in the bottom of the canon, and one of 
the hills formed by the debris is several hundred feet in height. 
The stream below the falls is so filled with boulders and falls 10 
to 20 feet in altitude that it is almost impassable. Ropes and 
scaling ladders would be required should one attempt to follow 
the actual course of the water. 
The height of the fall above the pool is 871 feet in a single 
perpendicular drop, and by going down the stream about 1,500 
feet sufficient additional fall is obtained to give a total head of 
nearly 1,200 feet. The quantity of water flowing at the time of 
my visit, which was in the dry season, was 125 cubic feet per 
minute, which would produce about 250 horse-power. The 
amount of water passing during the rainy season has not been 
measured, but the quantity is very great, as it comes from the 
rapid drainage of about 75 square miles above the falls. About 
6 miles down the canon there is another fall several hundred 
feet high which I did not see. 
It would be interesting to attempt to discuss the causes that 
produced this canon, but further than to suggest that it is the 
result of the gradual extension of a barranca or ravine, caused 
by surface washing that began on the Pacific Slope and slowly 
cut its way into the heart of the Sierras, until stopped by a por- 
phyry dike at the falls, I can advance no theory at present. 
The difficulty of making consecutive geological observations 
is very great,as may be inferred from the preceding and no data 
are obtainable upon which to base a more comprehensive ex- 
planation. The topography now shows the results of erosion 
by surface waters more strongly than the presence of faults or 
upheavals. 
A glance at the colored geological chart, made by the Mexican 
Government, will show many white or unexamined areas in this. 
