Geological researches in China, Mongolia, and Japan, during the years 1862-1865.

CHINA, MONGOLIA, AND JAPAN. 5
Flanking this granite core on both sides and covering it, is the great Devonian
limestone floor of the Chinese Coal measures. On the eastern flank of the granitic
axis the limestone strata trend, almost uniformly, N. E. S. W., varying in dip from
25~ to 8~ towards the S. E. as we recede from the granite. On the western flank
the strike is less regular, changing from nearly N. S., at the contact with the metamorphic schists, to N. E. S. W. in the upper part of the limestone. In the immediate neighborhood of the river, over an area of forty or fifty square miles, the
limestone has disappeared, but in the distance, on both sides of the Yangtse, its
yellow cliffs are seen towering to a height of more than 2,000 feet above the water.
I know of no limestone deposit that can rival this in thickness. Taking the
length of the cross section from its contact with the younger conglomerates, near
Ichang, to where it rests on the metamorphic schists, to be seven and one-half
geographic miles, and the mean dip at 150, viz., 100 for the eastern half and 200
for the western, we obtain the enormous thickness of 11,600 feet, more than two
statute miles. J. observed no faults in this gorge, and the great thickness observed
in this same limestone in Northern China, leads me to think that the above estimate
cannot be far from the truth.
West of this ridge of limestone is another of about the same size, the intervening space being occupied by the Coal measures.
Here, within a distance of eighty miles, are the principal rapids, while the river
traverses the limestone through a series of five gorges unsurpassed in the grandeur
of their scenery. Tie Yangtse, which, a few miles below the mouth of the Ichang
gorge, has a width of 960 yards, is in this narrowed to 250, and in the Fungsiang
gorge to 150 yards.1 In these narrow passages, whose walls are from 900 to 1200
feet high, cliffs of bare rock, often vertical or overhanging, alternate with steep
declivities clothed in green from the water to the summit, and with deep, inaccessible dells filled with the rich growth of a semi-tropical vegetation. Streams flowing
from the mouths of caverns high above the river, cool the air in their descent, while
the huge clusters of stalactite which they have formed-the work of ages-show
well the chemical power of the smallest drop, side by side with the mechanical force
of the rolling river. Through these gloomy chasms the skilful boatmen drag the
heavy junks, now " tracking" them from paths and steps hewn in the solid rock,
now pulling them by rusty and time-worn chains clamped along the vertical walls.
The depth of the water must be very great,2 and the difference between high
and low water is said to be as much as eighty feet in the Ichang gorge.
The limestone is generally of a bluish-gray color and compact texture, though
subordinate to this variety, layers occur having every shade of color and grain.
A gray, compact variety, with frequent large crystals of calcite is not uncommon; and a very compact, almost black kind is quarried in the Ichang gorge.
Indeed gray, pink, red, black, and blue varieties of this same limestone, with compact, porphyritic and crystalline textures, furnish in almost every province of China
1 Blackiston. Five months on the UTpper Yangtse.
2 Blackiston's party found no bottom with eighteen fathoms.