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； a perfect pavement became a sine qua non。 We have
secured this by the half…inch sheet of steel spread over a
carefully laid surface of asphalt； with but little bevel； and
though this might be slippery for horses' feet； it never
seriously affects our wheels。 There being nothing harder than
the rubber ties of comparatively light drays upon itfor the
heavy traffic is carried by electric railways under groundit
will practically never wear out。
〃With the application of steel to the entire surface； car…tracks
became unnecessary； ordinary wheels answering as well as those
with flanges； so that no new tracks were laid； and finally the
car companies tore up the existing ones； selling them in many
instances to the municipalities as old iron。 Our streets also
need but little cleaning； neither is the surface continually
indented； as the old cobble…stones and Belgian blocks were； by
the pounding of the horses' feet； so that the substitution of
electricity for animal power has done much to solve the problem
of attractive streets。
〃Scarcely a ton of coal comes to Manhattan Island or its vicinity
in a year。 Very little of it leaves the mines； at the mouths of
which it is converted into electricity and sent to the points of
consumption by wire； where it is employed for all uses to which
fuel was put； and many others。 Consequently there is no smoke；
and the streets are not encumbered with coal…carts； the entire
width being given up to carriages； etc。 The ground floors in the
business parts are used for large warehouses； trucks running in
to load and unload。 Pedestrians therefore have sidewalks level
with the second story； consisting of glass floors let into
aluminum frames； while all street crossings are made on bridges。
Private houses have a front door opening on the sidewalk； and
another on the ground level； so that ladies paying visits or
leaving cards can do so in carriages。 In business streets the
second story is used for shops。 In place of steel covering；
country roads have a thick coating of cement and asphalt over a
foundation of crushed stone； giving a capital surface； and have a
width of thirty…three feet （two rods） in thinly settled
districts； to sixty…six feet （four rods） where the population is
greater。 All are planted with shade and fruit trees； while the
wide driveways have one or two broad sidewalks。 The same rule of
making the slow…moving vehicles keep near the outside prevails；
though the rate of increase in speed on approaching the middle is
more rapid than in cities； and there is usually no dividing
ridge。 On reaching the top of a long and steep hill； if we do
not wish to coast； we convert the motors into dynamos； while
running at full speed； and so change the kinetic energy of the
descent into potential in our batteries。