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waterfalls, the last two do by far the most work. Much of the

electrical energy in every thunderstorm is also captured and

condensed in our capacious storage batteries, as natural hygeia

in the form of rain was and is still caught in our country

cisterns. Every exposed place is crowned by a cluster of huge

windmills that lift water to some pond or reservoir placed as

high as possible. Every stiff breeze, therefore, raises millions

of tons of water which operate hydraulic turbines as required.

Incidentally these storage reservoirs, by increasing the surface

exposed to evaporation and the consequent rainfall, have a very

beneficial effect on the dry regions in the interior of the

continent, and in some cases have almost superseded irrigation.

The windmill and dynamo thus utilize bleak mountain-tops that,

till their discovery, seemed to be but indifferent successes in

Dame Nature's domain. The electricity generated by these, in

connection with that obtained by waterfalls, tidal dynamos,

thunderstorms, chemical action, and slow-moving

quadruple-expansion steam engines, provides the power required to

run our electric ships and water-spiders, railways, and

stationary and portable motors, for heating the cables laid along

the bottom of our canals to prevent their freezing in winter, and

for almost every conceivable purpose. Sometimes a man has a

windmill on his roof for light and heat; then, the harder the

wintry blasts may blow the brighter and warmer becomes the house,

the current passing through a storage battery to make it more

steady. The operation of our ordinary electric railways is very

simple: the current is taken from an overhead, side, or

underneath wire, directly through the air, without the

intervention of a trolley, and the fast cars, for they are no

longer run in trains, make five miles a minute. The entire

weight of each car being used for its own traction, it can ascend

very steep grades, and can attain high speed or stop very

quickly.

"Another form is the magnetic railway, on which the cars are

wedge-shaped at both ends, and moved by huge magnets weighing

four thousand tons each, placed fifty miles apart. On passing a

magnet, the nature of the electricity charging a car is

automatically changed from positive to negative, or vice versa,

to that of the magnet just passed, so that it repels while the

next attracts. The successive magnets are charged oppositely,

the sections being divided halfway between by insulators, the

nature of the electricity in each section being governed by the

charge in the magnet. To prevent one kind of electricity from

uniting with and neutralizing that in the next section by passing

through the car at the moment of transit, there is a "dead

stretch" of fifty yards with rails not charged at all between the

sections. This change in the nature of the electricity is

repeated automatically every fifty miles, and obviates the

necessity of revolving machinery, the rails aiding communication.

"Magnetism being practically as instantaneous as gravitation, the

only limitations to speed are the electrical pressure at the

magnets, the resistance of the air, and the danger of the wheels

bursting from centrifugal force. The first can seemingly be

increased without limit; the atmospheric resistance is about to

be reduced by running the cars hermetically sealed through a

partial vacuum in a steel and toughened glass tube; while the

third has been removed indefinitely by the use of galvanized

aluminum, which bears about the same relation to ordinary

aluminum that steel does to iron, and which has twice the tensile

strength and but one third the weight of steel. In some cases

the rails are made turned in, so that it would be impossible for

a car to leave the track without the road-bed's being totally

demolished; but in most cases this is found to be unnecessary,

for no through line has a curve on its vast stretches with a

radius of less than half a mile. Rails, one hundred and sixty

pounds to the yard, are set in grooved steel ties, which in turn

are held by a concrete road-bed consisting of broken stone and

cement, making spreading rails and loose ballast impossible. A

large increase in capital was necessary for these improvements,

the elimination of curves being the most laborious part,

requiring bridges, cuttings, and embankments that dwarf the

Pyramids and would have made the ancient Pharaohs open their

eyes; but with the low rate of interest on bonds, the slight cost

of power, and great increase in business, the venture was a

success, and we are now in sight of further advances that will

enable a traveller in a high latitude moving west to keep pace

with the sun, and, should he wish it, to have unending day."

CHAPTER V.

DR. CORTLANDT'S HISTORY CONTINUED.

"In marine transportation we have two methods, one for freight

and another for passengers. The old-fashioned deeply immersed

ship has not changed radically from the steam and sailing vessels

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 as the crow flies, and without stopping, they reach a

destination in considerably shorter time.

Some passengers and express packages still cross the Atlantic on

'spiders,' but most of these light cargoes go in a far pleasanter

and more rapid way. The deep-displacement vessels, for heavy

freight, make little better speed than was made by the same class

a hundred years ago. But they are also run entirely by

electricity, largely supplied by wind, and by the tide turning

their motors, which become dynamos while at anchor in any stream.

They therefore need no bulky boilers, engines, sails, or

coal-bunkers, and consequently can carry unprecedentedly large

cargoes with comparatively small crews. The officers on the

bridge and the men in the crow's nest--the way to which is by a

ladder INSIDE the mast, to protect the climber from the

weather--are about all that is needed; while disablement is made

practically impossible, by having four screws, each with its own

set of automatically lubricating motors.

"This change, like other labour-saving appliances, at first

resulted in laying off a good many men, the least satisfactory

being the first to go; but the increase in business was so great

that the intelligent men were soon reemployed as officers at

higher rates of pay and more interesting work than before, while

they as consumers were benefited as much as any one else by the

decreased cost of production and transportation.

"With a view to facilitating interchange still further, our

Government has gradually completed the double coast-line that

Nature gave us in part. This was done by connecting islands

separated from shore by navigable water, and leaving openings for

ingress and exit but a few hundred yards wide. The breakwaters

required to do this were built with cribbing of incorrodible

metal, affixed to deeply driven metallic piles, and filled with

stones along coasts where they were found in abundance or excess.

This, while clearing many fields and improving them for

cultivation, provided just the needed material; since irregular

stones bind together firmly, and, while also insoluble, combine

considerable bulk with weight. South of Hatteras, where stones

are scarce, the sand dredged from parts of the channel was filled

into the crib, the surface of which has a concave metallic cover,

a trough of still water being often the best barrier against the

passage of waves. This double coast-line has been a great

benefit, and propelled vessels of moderate draught can range in

smooth water, carrying very full loads, from Labrador to the

Orinoco. The exits are, of course, protected by a line of

cribbing a few hundred feet to seaward.

"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. The power is applied

through turbine screws, half of which are capable of propelling

the flat deck in its inclined position at sufficient speed to

prevent its falling. The moving parts have ball bearings and

friction rollers, lubrication being secured automatically, when

required, by a supply of vaseline that melts if any part becomes

hot. All the framing is of thin but very durable galvanized

aluminum, which has superseded steel for every purpose in which

weight is not an advantage, as in the permanent way on railways.

The air ships, whose length varies from fifty to five hundred

feet, have rudders for giving a vertical or a horizontal motion,

and several strengthening keels that prevent leeway when turning.

They are entirely on the principle of birds, maintaining

themselves mechanically, and differing thus from the unwieldy

balloon. Starting as if on a circular railway, against the wind,

they rise to a considerable height, and then, shutting off the