—_ 
Fe. 24, 1870] 
NATURE 
435 
CANONS 
ie the south of Salt Lake and the Mormon Territory 
lies a dreary series of plateaux traversed by the 
Colorado river and its tributaries, which bear their burthen 
of waters into the Gulf of California. Though this region 
possesses many considerable streams, it is over large 
areas a kind of desolate wilderness, for instead of irri- 
gating the ground these streams flow in profound gorges, 
which serve as natural drains to carry off the water which 
may fall upon the tablelands. Many fabulous tales have 
been told of these regions, their natural marvels receiving 
many amplifications as they came to be rehearsed by 
Indians, trappers, and adventurous wanderers into the 
far west. In 1857 the Government of the United States 
despatched an expedition to explore that little known 
portion of the Continent, and the report published by the 
expedition in 1861 gave the first trustworthy and detailed 
markable gorge by the interesting narrative in Mr. Bell’s 
“New Tracks in North America,” and by the fuller de- 
tails, as yet only partially published, obtained by an 
exploring party under Colonel Powell, of the United 
States army. By successive travellers and Government 
expeditions the gorges of the Colorado had been reached 
here and there. The surveying party of 1857-58 mapped 
them out and gave many admirable drawings of them, 
but declared the river not to be navigable above the 
Black Cafion. Profiting by previous failures, and by all 
the information which he could receive from Indians 
and others, Colonel Powell conceived the bold idea of 
attempting the descent of the Colorado in boats. After 
months of toil and danger, he succeeded in forcing 
the passage of these forbidding gorges, and emerging 
safely at their further end. From his survey it appears 
that the Grand Cajion is 238 miles long, and from 2,500 
to 4,000 feet deep. But thouzh this is the longest, there 
HEAD OF MERCED AND TUOLUMNE kiveRs (See Geology of the Sierra Nevada in Whitney's 
Geological Survey of California, pp. 415—419) 
account of the Colorado region. The truth turned out to 
be almost stranger than the fiction. A vast territory was 
found to be intersected by ravines leading into the main line 
of gorges of the Colorado. These ravines, or cahons as 
they are termed, meander oyer the table-land as rivers do 
over alluvial meadows ; but they are thousands of feet 
ceep—hundreds of miles long, and so numerous that 
the country traversed by them is said to be impassable, 
save to the fowls of the air. 
The longest and deepest gorge is the Grand Canon of 
the Colorado. Its length was set down by Dr. Newberry 
as about 300 miles ; and its walls were described as rising 
steeply, sometimes vertically, from the margin of the river 
which filled the bottom of the ravine, to a height of from 
3,000 to 6,000 feet—a line of precipice or natural section 
which has not yet found its equal on any other part of the 
globe.* Attention has lately been again called to this re- 
* See Dr. Newberry’s section of this gorge in Nature, No. 6, p. 163. 
| are other ravines of hardly inferior dimensions. 
On the 
Green River, Col. Powell’s party navigated a series 190 
miles long. From where the Green River joins the Colo- 
rado, they passed through a succession of canons for a dis- 
tance of 256 miles before they came to the Grand Cajon. 
Each canon has tributary canons: these again have 
often also their tributaries. In some places the lateral 
gorges crowd so closely together where they join the main 
one, that they are divided by perpendicular walls of rock, 
which seem so narrow at top as hardly to furnish footing 
for a man, though in reality large enough to support cathe- 
drals. And these walls shoot 2,000 or 3,000 feet above the 
river, “ while rocks and crags and peaks rise still higher, 
away back from the river, until they reach an altitude of 
nearly 5,000 feet.” They consist to a large extent of 
brown, grey, and orange-coloured sandstones, gently in- 
clined or horizontal, beneath which marble and granite in 
some places have been deeply trenched. In some places 
