"The rocks have been removed from all channels about New York and
other commercial centres, while the shallow places have been
dredged to a uniform depth. This diminishes the dangers of
navigation and considerably decreases the speed with which the
tides rush through. Where the obstructions consisted of reefs
surrounded by deep water, their removal with explosives was easy,
the shattered fragments being allowed to sink to the bottom and
remain there beneath the danger line.
"Many other great works have also been completed. The canals at
Nicaragua have been in operation many years, it having been found
best to have several sizes of locks, and to use the large ones
only for the passage of large vessels. The improved Erie and
Champlain Canals also enable ships four hundred feet long to
reach New York from the Great Lakes via the Hudson River.
"For flying, we have an aeroplane that came in when we devised a
suitable motor power. This is obtained from very light
paper-cell batteries that combine some qualities of the primary
and secondary type, since they must first be charged from a
dynamo, after which they can supply full currents for one hundred
hours--enough to take them around the globe--while partly
consuming the elements in the cells.
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