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 batteries, coast down the aerial slope at a rate that sometimes touches five hundred miles an hour. When near the ground the helmsman directs the prow upward, and, again turning on full current, rushes up the slope at a speed that far exceeds the eagle's, each drop of two miles serving to take the machine twenty or thirty; though, if the pilot does not wish to soar, or if there is a fair wind at a given height, he can remain in that stratum of the atmosphere by moving horizontally. He can also maintain his elevation when moving very slowly, and though the headway be entirely stopped, the descent is gradual on account of the aeroplane's great spread, the batteries and motors being secured to the under side of the deck.
"The motors are so light that they develop two horse power for every pound of their weight; while, to keep the frames thin, the necessary power is obtained by terrific speed of the moving parts, as though a steam engine, to avoid great pressure in its cylinders, had a long stroke and ran at great piston speed, which, however, is no disadvantage to the rotary motion of the electric motor, there being no reciprocating cranks, etc., that must be started and stopped at each revolution.
"To obviate the necessity of gearing to reduce the number of revolutions to those possible for a large screw, this member is made very small, and allowed to revolve three thousand times a minute, so that the requisite power is obtained with great simplicity of mechanism, which further decreases friction. The shafts, and even the wires connecting the batteries with the motors, are made large and hollow. Though the primary battery pure and simple, as the result of great recent advances in chemistry, seems to be again coming up, the best aeroplane batteries are still of the combination-storage type. These have been so perfected that eight ounces of battery yield one horse power for six hours, so that two pounds of battery will supply a horse power for twenty-four hours; a small fifty-horse-power aeroplane being therefore able to fly four days with a battery weight of but four hundred pounds.
"Limestone and clarified acid are the principal parts of these batteries. It was known long ago that there was about as much imprisoned solar energy in limestone as in coal, but it was only recently that we discovered this way of releasing and using it.
"Common salt plays an important part in many of our chemical reactions. By combining it with limestone, and treating this with acid jelly, we also get good results on raising to the boiling-point.
"However enjoyable the manly sport of yachting is on water, how vastly more interesting and fascinating it is for a man to have a yacht in which he can fly to Europe in one day, and with which the exploration of tropical Africa or the regions about the poles is mere child's play, while giving him so magnificent a bird's-eye view! Many seemingly insoluble problems are solved by the advent of these birds. Having as their halo the enforcement of peace, they have in truth taken us a long step towards heaven, and to the co-operation and higher civilization that followed we shall owe much of the success of the great experiment on Mother Earth now about to be tried.
"Another change that came in with a rush upon the discovery of a battery with insignificant weight, compact form, and great capacity, was the substitution of electricity for animal power for the movement of all vehicles. This, of necessity brought in good roads, the results obtainable on such being so much greater than on bad ones that a universal demand for them arose. This was in a sense cumulative, since the better the
