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[Illustration: ORVILLE WRIGHT IN THE 80-MILE-AN-HOUR “BABY WRIGHT”
RACER.]




  How It Flies

  or,

  THE CONQUEST OF THE AIR

  The Story of Man’s Endeavors to Fly and of the
  Inventions by which He Has Succeeded

  By

  RICHARD FERRIS, B.S., C.E.

  Illustrated by Over One Hundred and Fifty Half-tones and Line
  Drawings, Showing the Stages of Development from the
  Earliest Balloon to the Latest Monoplane and Biplane

  New York

  THOMAS NELSON AND SONS

  381-385 Fourth Avenue


Copyright, 1910, by

THOMAS NELSON & SONS


THE TROW PRESS, NEW YORK




PREFACE


In these pages, by means of simple language and suitable pictures, the
author has told the story of the Ships of the Air. He has explained
the laws of their flight; sketched their development to the present
day; shown how to build the flying machine and the balloon, and how
to operate them; recounted what man has done, and what he hopes to do
with their aid. In a word, all the essential facts that enter into the
Conquest of the Air have been gathered into orderly form, and are here
presented to the public.

We who live to-day have witnessed man’s great achievement; we have seen
his dream of ages come true. Man has learned to _fly_!

The air which surrounds us, so intangible and so commonplace that
it seldom arrests our attention, is in reality a vast, unexplored
ocean, fraught with future possibilities. Even now, the pioneers of
a countless fleet are hovering above us in the sky, while steadily,
surely these wonderful possibilities are unfolded.

The Publishers take pleasure in acknowledging their indebtedness to the
_Scientific American_ for their courtesy in permitting the use of many
of the illustrations appearing in this book.

NEW YORK, October 20, 1910.




CONTENTS


  CHAPTER                                       PAGE

        PREFACE                                    7

     I. INTRODUCTORY                              11

    II. THE AIR                                   20

   III. LAWS OF FLIGHT                            37

    IV. FLYING MACHINES                           55

     V. FLYING MACHINES: THE BIPLANE              78

    VI. FLYING MACHINES: THE MONOPLANE           112

   VII. FLYING MACHINES: OTHER FORMS             141

  VIII. FLYING MACHINES: HOW TO OPERATE          151

    IX. FLYING MACHINES: HOW TO BUILD            174

     X. FLYING MACHINES: MOTORS                  193

    XI. MODEL FLYING MACHINES                    215

   XII. THE GLIDER                               241

  XIII. BALLOONS                                 257

    XIV. BALLOONS: THE DIRIGIBLE                 296

     XV. BALLOONS: HOW TO OPERATE                340

    XVI. BALLOONS: HOW TO MAKE                   351

   XVII. MILITARY AERONAUTICS                    363

  XVIII. BIOGRAPHIES OF PROMINENT AERONAUTS      379

    XIX. CHRONICLE OF AVIATION ACHIEVEMENTS      407

     XX. EXPLANATION OF AERONAUTICAL
               TERMS                             452




HOW IT FLIES




Chapter I.

INTRODUCTORY.

    The sudden awakening--Early successes--Influence of the gasoline
    engine on aeroplanes--On dirigible balloons--Interested
    inquiry--Some general terms defined.


In the year 1908 the world awakened suddenly to the realization that at
last the centuries of man’s endeavor to fly mechanically had come to
successful fruition.

There had been a little warning. In the late autumn of 1906,
Santos-Dumont made a flight of 720 feet in a power-driven machine.
There was an exclamation of wonder, a burst of applause--then a relapse
into unconcern.

In August, 1907, Louis Bleriot sped free of the ground for 470 feet;
and in November, Santos-Dumont made two flying leaps of barely 500
feet. That was the year’s record, and it excited little comment. It is
true that the Wright brothers had been making long flights, but they
were in secret. There was no public knowledge of them.

In 1908 came the revelation. In March, Delagrange flew in a Voisin
biplane 453 feet, carrying Farman with him as a passenger. Two weeks
later he flew alone nearly 2½ miles. In May he flew nearly 8 miles. In
June his best flight was 10½ miles. Bleriot came on the scene again
in July with a monoplane, in which he flew 3¾ miles. In September,
Delagrange flew 15 miles--in less than 30 minutes. In the same month
the Wrights began their wonderful public flights. Wilbur, in France,
made records of 41, 46, 62, and 77 miles, while Orville flew from 40 to
50 miles at Fort Myer, Va. Wilbur Wright’s longest flight kept him in
the air 2 hours and 20 minutes.

The goal had been reached--men had achieved the apparently impossible.
The whole world was roused to enthusiasm.

Since then, progress has been phenomenally rapid, urged on by the
striving of the inventors, the competition of the aircraft builders,
and the contests for records among the pilots.

By far the largest factor in the triumph of the aeroplane is the
improved gasoline engine, designed originally for automobiles. Without
this wonderful type of motor, delivering a maximum of power with a
minimum of weight, from concentrated fuel, the flying machine would
still be resting on the earth.

[Illustration: The Renard and Krebs airship _La France_, at
Chalais-Meudon.]

Nor has the influence of the gasoline motor been much less upon that
other great class of aircraft, the dirigible balloon. After 1885, when
Renard and Krebs’ airship _La France_ made its two historic voyages
from Chalais-Meudon to Paris, returning safely to its shed, under the
propulsion of an electric motor, the problem of the great airship lay
dormant, waiting for the discovery of adequate motive power. If the
development of the dirigible balloon seems less spectacular than that
of the aeroplane, it is because the latter had to be created; the
dirigible, already in existence, had only to be revivified.

Confronted with these new and strange shapes in the sky, some making
stately journeys of hundreds of miles, others whirring hither and
thither with the speed of the whirlwind, wonder quickly gives way to
the all-absorbing question: _How do they fly?_ To answer fully and
satisfactorily, it seems wise, for many readers, to recall in the
succeeding chapters some principles doubtless long since forgotten.

       *       *       *       *       *

As with every great advance in civilization, this expansion of the
science of aeronautics has had its effect upon the language of the day.
Terms formerly in use have become restricted in application, and other
terms have been coined to convey ideas so entirely new as to find no
suitable word existent in our language. It seems requisite, therefore,
first to acquaint the reader with clear definitions of the more common
terms that are used throughout this book.

_Aeronautics_ is the word employed to designate the entire subject of
aerial navigation. An _aeronaut_ is a person who sails, or commands,
any form of aircraft, as distinguished from a passenger.

_Aviation_ is limited to the subject of flying by machines which are
not floated in the air by gas. An _aviator_ is an operator of such
machine.

[Illustration: A free balloon, with parachute.]

Both aviators and aeronauts are often called _pilots_.

A _balloon_ is essentially an envelope or bag filled with some gaseous
substance which is lighter, bulk for bulk, than the air at the surface
of the earth, and which serves to float the apparatus in the air. In
its usual form it is spherical, with a car or basket suspended below
it. It is a _captive balloon_ if it is attached to the ground by a
cable, so that it may not rise above a certain level, nor float away in
the wind. It is a _free balloon_ if not so attached or anchored, but is
allowed to drift where the wind may carry it, rising and falling at the
will of the pilot.

[Illustration: A dirigible balloon.]

A _dirigible balloon_, sometimes termed simply a dirigible, usually has
its gas envelope elongated in form. It is fitted with motive power to
propel it, and steering mechanism to guide it. It is distinctively the
_airship_.

_Aeroplanes_ are those forms of flying machines which depend for their
support in the air upon the spread of surfaces which are variously
called wings, sails, or planes. They are commonly driven by propellers
actuated by motors. When not driven by power they are called _gliders_.

[Illustration: A biplane glider.]

Aeroplanes exist in several types: the _monoplane_, with one spread
of surface; the _biplane_, with two spreads, one above the other; the
_triplane_, with three spreads, or decks; the _multiplane_, with more
than three.

The _tetrahedral plane_ is a structure of many small cells set one upon
another.

_Ornithopter_ is the name given to a flying machine which is operated
by flapping wings.

[Illustration: A parachute descending.]

_Helicopter_ is used to designate machines which are lifted vertically
and sustained in the air by propellers revolving in a horizontal plane,
as distinguished from the propellers of the aeroplane, which revolve in
vertical planes.

A _parachute_ is an umbrella-like contrivance by which an aeronaut may
descend gently from a balloon in mid-air, buoyed up by the compression
of the air under the umbrella.

For the definition of other and more technical terms the reader is
referred to the carefully prepared Glossary toward the end of the book.




Chapter II.

THE AIR.

    Intangibility of air--Its
    substance--Weight--Extent--Density--Expansion
    by heat--Alcohol fire--Turbulence of the
    air--Inertia--Elasticity--Viscosity--Velocity of
    winds--Aircurrents--Cloud levels--Aerological stations--High
    altitudes--Practical suggestions--The ideal highway.


The air about us seems the nearest approach to nothingness that we know
of. A pail is commonly said to be empty--to have nothing in it--when it
is filled only with air. This is because our senses do not give us any
information about air. We cannot see it, hear it, touch it.

When air is in motion (wind) we hear the noises it makes as it passes
among other objects more substantial; and we feel it as it blows by us,
or when we move rapidly through it.

We get some idea that it exists as a substance when we see dead leaves
caught up in it and whirled about; and, more impressively, when in the
violence of the hurricane it seizes upon a body of great size and
weight, like the roof of a house, and whisks it away as though it were
a feather, at a speed exceeding that of the fastest railroad train.

In a milder form, this invisible and intangible air does some of our
work for us in at least two ways that are conspicuous: it moves ships
upon the ocean, and it turns a multitude of windmills, supplying the
cheapest power known.

That this atmosphere is really a fluid ocean, having a definite
substance, and in some respects resembling the liquid ocean upon which
our ships sail, and that we are only crawling around on the bottom
of it, as it were, is a conception we do not readily grasp. Yet this
conception must be the foundation of every effort to sail, to fly, in
this aerial ocean, if such efforts are to be crowned with success.

As a material substance the air has certain physical properties, and
it is the part of wisdom for the man who would fly to acquaint himself
with these properties. If they are helpful to his flight, he wants to
use them; if they hinder, he must contrive to overcome them.

In general, it may be said that the air, being in a gaseous form,
partakes of the properties of all gases--and these may be studied
in any text-book on physics, Here we are concerned only with those
qualities which affect conditions under which we strive to fly.

Of first importance is the fact that air has _weight_. That is, in
common with all other substances, it is attracted by the mass of the
earth exerted through the force we call gravity. At the level of the
sea, this attraction causes the air to press upon the earth with a
weight of nearly fifteen pounds (accurately, 14.7 lbs.) to the square
inch, when the temperature is at 32° F. That pressure is the weight of
a column of air one inch square at the base, extending upward to the
outer limit of the atmosphere--estimated to be about 38 miles (some say
100 miles) above sea-level. The practical fact is that normal human
life cannot exist above the level of 15,000 feet, or a little less than
three miles; and navigation of the air will doubtless be carried on at
a much lower altitude, for reasons which will appear as we continue.

The actual weight of a definite quantity of dry air--for instance,
a cubic foot--is found by weighing a vessel first when full of air,
and again after the air has been exhausted from it with an air-pump.
In this way it has been determined that a cubic foot of dry air,
at the level of the sea, and at a temperature of 32° F., weighs 565
grains--about 0.0807 lb. At a height above the level of the sea, a
cubic foot of air will weigh less than the figure quoted, for its
density decreases as we go upward, the pressure being less owing to
the diminished attraction of the earth at the greater distance. For
instance, at the height of a mile above sea-level a cubic foot of air
will weigh about 433 grains, or 0.0619 lb. At the height of five miles
it will weigh about 216 grains, or 0.0309 lb. At thirty-eight miles
it will have no weight at all, its density being so rare as just to
balance the earth’s attraction. It has been calculated that the whole
body of air above the earth, if it were all of the uniform density of
that at sea-level, would extend only to the height of 26,166 feet.
Perhaps a clearer comprehension of the weight and pressure of the ocean
of air upon the earth may be gained by recalling that the pressure of
the 38 miles of atmosphere is just equal to balancing a column of water
33 feet high. The pressure of the air, therefore, is equivalent to the
pressure of a flood of water 33 feet deep.

[Illustration: Comparative Elevations of Earth and Air.]

But air is seldom dry. It is almost always mingled with the vapor
of water, and this vapor weighs only 352 grains per cubic foot at
sea-level. Consequently the mixture--damp air--is lighter than dry air,
in proportion to the moisture it contains.

[Illustration: Apparatus to show effects of heat on air currents. _a_,
alcohol lamp; _b_, ice. The arrows show direction of currents.]

Another fact very important to the aeronaut is that the air is in
_constant motion_. Owing to its ready expansion by heat, a body of
air occupying one cubic foot when at a temperature of 32° F. will
occupy more space at a higher temperature, and less space at a lower
temperature. Hence, heated air will flow upward until it reaches a
point where the natural density of the atmosphere is the same as its
expanded density due to the heating. Here another complication comes
into play, for ascending air is cooled at the rate of one degree for
every 183 feet it rises; and as it cools it grows denser, and the speed
of its ascension is thus gradually checked. After passing an altitude
of 1,000 feet the decrease in temperature is one degree for each 320
feet of ascent. In general, it may be stated that air is expanded
one-tenth of its volume for each 50° F. that its temperature is raised.

This highly unstable condition under ordinary changes of temperature
causes continual movements in the air, as different portions of it are
