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EAST ASIA.
THE GREAT WALL.
The border-line between Mongolia and China proper was formerly indicated by
the Great Wall, which, including all its windings and the double and triple lines
erected at some points, has a total length of about 2,000 miles. Allowing a mean
height of no more than 26 feet and a width of 20 feet, this prodigious structure
will represent a solid mass of some 4,000 million cubic feet of masonry. Those
who assert that the Great Wall was of no more practical use than the pyramids of
Fig. 42. THE GKEAT WALL. VIEW TAKEN AT THE NANKOW PASS.
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Egypt forget that for many centuries it served to arrest the military expeditions
of the Iliungnu, ancestors of the present Mongolians. The sentinels mounting
guard on the towers erected at intervals along the ramparts gave timely warning
of the enemy's approach, while all the natural passages were guarded by encamp-
ments. Every gate had its little garrison, around which towns soon sprang up,
serving as market-places for the surrounding populations.
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Sheltered behind these