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 All the framing is of thin but very durable galvanized aluminum, which has superseded steel for every purpose in which weight is not an advantage, as in the permanent way on railways.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 streets and roads became, the greater the inducement to have an electric carriage. The work of opening up the country far and near, by straightening and improving existing roads, and laying out new ones that combine the solidity of the Appian Way with the smoothness of modern asphalt, was largely done by convicts, working under the direction of State and Government engineers. Every State contained a horde of these unprofitable boarders, who, as they formerly worked, interfered with honest labour, and when idle got into trouble. City streets had been paved by the municipality; country roads attended to by the farmers, usually very unscientifically. Here was a field in which convict labour would not compete, and an important work could be done. When once this was made the law, every year showed improvement, while the convicts had useful and healthful occupation.
"The electric phaetons, as those for high speed are called, have three and four wheels, and weigh, including battery and motor, five hundred to four thousand pounds. With hollow but immensely strong galvanically treated aluminum frames and pneumatic or cushion tires, they run at thirty-five and forty miles an hour on country roads, and attain a speed over forty on city streets, and can maintain this rate without recharging for several days. They can therefore roam over the roads of the entire hemisphere, from the fertile valley of the Peace and grey shores of Hudson Bay, to beautiful Lake Nicaragua, the River Plate, and Patagonia, improving man by bringing him close to Nature, while they combine the sensations of coasting with the interest of seeing the country well.
"To recharge the batteries, which can be done in almost every town and village, two copper pins attached to insulated copper wires are shoved into smooth-bored holes. These drop out of themselves by fusing a small lead ribbon, owing to the increased resistance, when the acid in the batteries begins to 'boil,' though there is, of course, but little heat in this, the function of charging being merely to bring about the condition in which part of the limestone can be consumed, the batteries themselves, when in constant use, requiring to be renewed about once a month. A handle at the box seat turns on any part of the attainable current, for either going ahead or reversing, there being six or eight degrees of speed for both directions, while the steering is done with a small wheel.
"Light but powerful batteries and motors have also been fitted on bicycles, which can act either as auxiliaries for hill-climbing or in case of head wind, or they can propel the machine altogether.
"Gradually the width of the streets became insufficient for the traffic, although the elimination of horses and the consequent increase in speed greatly augmented their carrying capacity, until recently a new system came in. The whole width of the avenues and streets in the business parts of the city, including the former sidewalks, is given up to wheel traffic, an iron ridge extending along the exact centre to compel vehicles to keep to the right. Strips of nickel painted white, and showing a bright phosphorescence at night, are let into the metal pavement flush with the surface, and run parallel to this ridge at distances of ten to fifteen feet, dividing each half of the avenue into four or five sections, their width increasing as they approach the middle. All trucks or drays moving at less than seven miles an hour are obliged to keep in the section nearest the building line, those running between seven and fifteen in the next, fifteen to twenty-five in the third, twenty-five to thirty-five in the fourth, and everything faster than that in the section next the ridge, unless the avenue or street is wide enough for further subdivisions. If it is wide enough for only four or less, the fastest vehicles must keep next the middle, and limit their speed to the rate allowed in that section, which is marked at every crossing in white letters sufficiently large for him that runs to read. It is therefore only in the wide thoroughfares that very high speed can be attained. In addition to the crank that corresponds to a throttle, there is a gauge on every vehicle, which shows its exact speed in miles per hour, by gearing operated by the revolutions of the wheels.
"The policemen on duty also have instantaneous kodaks mounted on tripods, which show the position of any carriage at half- and quarter-second intervals, by which it is easy to ascertain the exact speed, should the officers be unable to judge it by the eye; so there is no danger of a vehicle's speed exceeding that allowed in the section in which it happens to be; neither can a slow one remain on the fast lines.
"Of course, to make such high speed for ordinary carriages possible,