第13章 BOOK I.(12)

"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vaseline that melts if any part becomes hot.All the framing is of thin but very durable galvanized aluminum,which has superseded steel for every purpose in which weight is not an advantage,as in the permanent way on railways.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 streets and roads became,the greater the inducement to have an electric carriage.