A Journey in Other Worlds [15]
of the last century, except that electricity has superseded all
other motive powers. Steamers gradually passed through the five
hundred-, six hundred-, and seven hundred-foot-long class, with
other dimensions in proportion, till their length exceeded one
thousand feet. These were very fast ships, crossing the Atlantic
in four and a half days, and were almost as steady as houses, in
even the roughest weather.
"Ships at this period of their development had also passed
through the twin and triple screw stage to the quadruple, all
four together developing one hundred and forty thousand indicated
horse-power, and being driven by steam. This, of course,
involved sacrificing the best part of the ship to her engines,
and a very heavy idle investment while in port. Storage
batteries, with plates composed of lead or iron, constantly
increasing in size, had reached a fair state of development by
the close of the nineteenth century.
"During the second decade of the twentieth century the engineers
decided to try the plan of running half of a transatlantic
liner's screws by electricity generated by the engines for
driving the others while the ship was in port, this having been a
success already on a smaller scale. For a time this plan gave
great satisfaction, since it diminished the amount of coal to be
carried and the consequent change of displacement at sea, and
enabled the ship to be worked with a smaller number of men. The
batteries could also, of course, be distributed along the entire
length, and placed where space was least valuable.
"The construction of such huge vessels called for much
governmental river and harbour dredging, and a ship drawing
thirty-five feet can now enter New York at any state of the tide.
For ocean bars, the old system of taking the material out to sea
and discharging it still survives, though a jet of water from
force-pumps directed against the obstruction is also often
employed with quick results. For river work we have discovered a
better method. All the mud is run back, sometimes over a mile
from the river bank, where it is used as a fertilizer, by means
of wire railways strung from poles. These wire cables combine in
themselves the functions of trolley wire and steel rail, and
carry the suspended cars, which empty themselves and return
around the loop for another load. Often the removed material
entirely fills small, saucer-shaped valleys or low places, in
which case it cannot wash back. This improvement has ended the
necessity of building jetties.
"The next improvement in sea travelling was the 'marine spider.'
As the name shows, this is built on the principle of an insect.
It is well known that a body can be carried over the water much
faster than through it. With this in mind, builders at first
constructed light framework decks on large water-tight wheels or
drums, having paddles on their circumferences to provide a hold
on the water. These they caused to revolve by means of machinery
on the deck, but soon found that the resistance offered to the
barrel wheels themselves was too great. They therefore made them
more like centipeds with large, bell-shaped feet, connected with
a superstructural deck by ankle-jointed pipes, through which,
when necessary, a pressure of air can be forced down upon the
enclosed surface of water. Ordinarily, however, they go at great
speed without this, the weight of the water displaced by the bell
feet being as great as that resting upon them. Thus they swing
along like a pacing horse, except that there are four rows of
feet instead of two, each foot being taken out of the water as it
is swung forward, the first and fourth and second and third rows
being worked together. Although, on account of their size, which
covers several acres, they can go in any water, they give the
best results on Mediterraneans and lakes that are free from ocean
rollers, and, under favourable conditions, make better speed than
the nineteenth-century express trains, and, of course, going
straight