164 
NATURE 
with great rapidity. 
changing the face of the country: 
obliterating valleys, 
[ Dec. 9, 1869 
This powerful agent is stated to be In the valley beyond this cafion, nearly all the water of 
the Aravaypa sinks into the earth. But the canon of 
levelling hills, turning rivers from their course, and ! canons is the great cafion of the Colorada, discovered by 
covering fertile 
tracts miles in 
extent with bare 
heaps of gravel. 
The most dis- 
tinctive features 
of the great basin 
are the canons, 
those narrow, 
deep, abrupt, and 
continous chasms 
at the bottom of 
many of which 
run rapid rivers, 
unapproachable 
by man or ani- 
mal, They are 
due to the action 
of water, being 
formed by the 
passage through 
a dry region of 
never-failing and 
rapid streams, 
coming from dis- 
tant sources ex- 
terior to the dry country. The water has worn its way in 
some instances through 1,000 ft. of granite. 
deep cuttings abound, the country is sterile, for they drain 
it to the utter- 
most, and the 
streams lie far 
below the reach 
of surface animal 
or vegetable life. 
One cafion, that 
of the Purgatoire, 
has been so 
named because 
of the “bright, 
fiery - red sand- 
stone” of which 
its walls are com- 
posed; the effect 
of the mass of 
colour is said to 
be wonderful. In 
another, the Ara- 
vaypa, a cliff be- 
low the average, 
was measured, 
and found to be 
825 ft. high. 
Here, when the 
sun had Jeft the 
upper world, and 
night had really 
come, the blackness of darkness around was something awful, 
and the stars which covered the narrow streak of sky above 
seemed to change the heavens into a zigzag belt, every inch of 
Which was radiant with diamonds. 
Where these 
MUSHROOM ROCK 
THE CEREUS GIGAN 
on. 
Earthquakes are frequent; 
Lopez de Car- 
denas in 1540, 
which is but 100 
feet wide at its 
narrowest, while 
its greatest depth 
has been _baro- 
metrically ascer- 
tained to be 7,000 
feet, or one mile 
and a third. The 
sun only shines 
into this terrible 
chasm for an 
hour a day, and 
it is 550 miles 
long. At its bot- 
tom runs the 
swift river from 
which it takes its 
name. The ac- 
count which Dr. 
Bell gives of 
James White's 
flight for life 
down this previ- 
ously unexplored cafion on a raft, makes a wonderful sen- 
sation story, which appears to have found believers. 
We reproduce from Dr. Bell’s book a geological section of 
this remarkable 
gorge. 
The alkali flats 
form another dis- 
tinctive feature in 
the basin. They 
are covered with 
salts, usually ni- 
trate of soda, and 
being _ perfectly 
barren, form 
white glistening 
sheets which, in 
the dry unsteady 
atmosphere of 
the desert, be- 
come tantalising 
mirages. The 
plateaux of the 
basin region were 
the last portions 
of the West 
which were raised 
from the sea; 
even now subter- 
ranean fires are 
active, and it is 
quite possible that gradual upheaval may be still going 
mud-volcanoes are 
still to be found in places; huge surface cracks have 
