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THE CONQUEST OF THE AIR




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THE CONQUEST OF THE AIE

OR THE
ADVENT OF AERIAL NAVIGATION



BY



A. LAWRENCE ROTCH, S.B., A.M.

Author of " Sounding the Ocean of Air"

Founder and Director of Blue Hill Meteorological Observatory,
Professor of Meteorology in Harvard University, Honorary
Member of the English, Austrian and German Meteor-
ological Societies, Corresponding Member of the
Berlin Aeronautical Society, Member of the
International Commission for Scientific
Aeronautics and of the Permanent
International Aeronautical
Commission, etc.



ILLUSTRATED




NEW YORK
MOFFAT, YARD AND COMPANY

1909



/



COPYRIGHT, 1909, BY
MOFFAT, YARD AND COMPANY

NEW YoK

All rights reserved
Published, September, 1909



THE QUINN & BODEN CO. PRESS
RAHWAY, N. J.



CONTENTS



PAGE



I. THE OCEAN OF AIR . i

II. THE HISTORY OF AEROSTATION . 38

III. THE DIRIGIBLE BALLOON . 78

IV. THE FLYING MACHINE 125
V. THE FUTURE OF AERIAL NAVIGA-
TION . 167



361841



LIST OF ILLUSTRATIONS

Orville Wright's Flight at Fort Myer, Va., Sept. 9,

1908 . Frontispiece

?AGE

Fig. r. Comparative Altitudes 5

Fig. 2. Annual Isotherms at St. Louis . . 10
Fig. 3. Diurnal Temperatures at Different

Heights 14

Fig. 4. Vertical Gradients above Blue Hill . . 16

Fig. 5. Sea of Clouds Seen from a Balloon . 19
Fig. 6. Diurnal Wind-Velocities at Different

Heights 21

Fig. 7. Courses of Ballons-Sondes from St.

Louis 28

Fig. 8. Trade and Counter-Trade Winds . . .34

Fig. 9. Lana's Airship 40

Fig. 10. Besnier's Flying-Machine .... 41
Fig. ii. First Aerial Voyage . . . . .50

Fig. 12. Second Aerial Voyage .... 56
Fig. 13. Jeffries and Blanchard Arriving in

France 63

Fig. 14. Highest Ascent of Glaisher and Coxwell 65

Fig. 15. Ascent of Preussen 66

Fig. 16. Ballon-Sondc Rising from St. Louis . 67

Fig. 17. Captive Balloon at Battle of Fleurus . 70

Fig. 18. Military Kite-Balloon 71

Fig. 19. The France over Paris .... 84
vii



vin ILLUSTRATIONS

PAGE

Fig. 20. Car of the Patrie 93

Fig. 21. Military Dirigible the Republique . . 95
Fig. 22. Dirigible, Clement-Bayard .... 99
Fig. 2-3. Zeppelin IV. on Lake Constance . . 105
Fig. 24. Zeppelin IV. in the Air .... 109

Fig. 25. Voyage of Zeppelin IV in

Fig. 26. Gross II. and Parseval II. at Tegel . 115
Fig. 27. Signal Corps Dirigible No. i . . .119
Fig. 28. Langley Aerodrome in Flight . . . 137
Fig. 29. Lilienthal Glider Descending . . . 139
Fig. 30. Wright Glider Descending . . .142
Fig. 31. Voisin Aeroplane in Flight . . . 146
Fig. 32. Wright Aeroplane in Position to Start . 150
Fig. 33. Details of Wright Aeroplane . . .152
Fig. 34. Esnault-Pelterie Monoplane about to

Leave the Ground 157

Fig. 35. June-Bug in Flight 162



PREFACE

THE final conquest of the air by man finds
no popular and, at the same time, scientific
account, in English, of its accomplishment.
While the rapid progress which is daily being
made in aerial navigation necessarily renders
any permanent record of the latest achieve-
ments impossible, yet the epoch when me-
chanical flight was demonstrated to the world
seems opportune to chronicle the past and
present status of the art and to forecast its
future.

The physical conditions which prevail in
the ocean of air being even more important to
the aeronaut than the conditions on bodies of
water are to the sailor, a knowledge of the
former is of vital interest. Accordingly, it ap-
peared appropriate that, at the outset, there
should be given a description of the ocean
above our heads, including the surveys and
soundings which have been executed by the
author during the past twenty years at his own
ix



x PREFACE

observatory. These and similar meteorological
researches, also undertaken elsewhere in the
interest of pure science, now become of prac-
tical value to the aerial traveler.

The general facts concerning aerial naviga-
tion have been derived at first hand from au-
thorities in Europe and America, the data are
quoted from reliable sources, and the illustra-
tions are reproduced from materials col-
lected by the author or from the best pictures
that have been published in foreign periodicals.
Mr. Octave Chanute, of Chicago, whose knowl-
edge of aeronautics is unsurpassed, has kindly
consented to read the proof-sheets.

BLUE HILL METEOROLOGICAL OBSERVATORY,

MILTON, MASS.
April, 1909.



CHAPTER I

THE OCEAN OF AIR

BEFORE discussing the methods of aerial
navigation, it will be advantageous to consider
the medium in which this must take place.
The atmospheric ocean, at the bottom of which
we live and move and have our being, presents
analogies to the aqueous ocean upon which it
rests. The lower portion of the former and the
upper surface of the latter we know best, and it
was to aid marine navigation that contiguous
currents in both oceans were determined. By
means of government expeditions, likewise, the
depths, thermometric and hydrometric condi-
tions of the oceans traversed by ships have
been ascertained, but the ocean above our heads
has been explored almost entirely in the inter-
est of pure science and without the expectation
of practical benefits. Apart from observations
on mountain-tops, which give results that do
not represent the conditions of the free air, the
study of the high atmosphere has been under-



2 THE 'CONQUEST OF THE AIR

taken systematically only within the past fif-
teen years and the fact that the atmosphere has
no boundaries and can be pre-empted by no
nation makes its exploration a truly interna-
tional undertaking. This is being done through
monthly kite and balloon ascensions under the
auspices of the International Commission for
Scientific Aeronautics, and the field of survey
has lately been extended to Asia and Africa
and the tropical and arctic oceans. The first
meteorological records with kites were ob-
tained at Blue Hill Observatory, near Bos-
ton, in 1894; the method was used at sea by
the author in 1901, and three years later the
temperature 10 'miles above the American
continent was -ascertained by means of sound-
ing balloons sent up under his direction. At
the present time the aero-physical observatory
of the United States Weather Bureau is mak-
ing daily kite flights and the extraordinary
height of more than four miles has been at-
tained. From all these sources many data are
being, accumulated which, while primarily in-
tended to increase our knowledge of the
physics of the globe, will also prove as useful
to the aerial voyager as are the ocean pilot
charts to the mariner.



THE OCEAN OF AIR 3

Let us now compare, in a general way, the
aerial and aqueous oceans. The former com-
pletely envelops the globe and rests lightly
upon the other ocean that covers the greater
portion of the crust with its tremendous
weight. The atmosphere extends with dimin-
ishing density to an indefinite height, while the
lesser depths of the sea are absolutely defined.
Both oceans receive their heat from the sun,
chiefly by radiation and absorption at their
junction with each other, and therefore both
become colder as we penetrate into them, so
that near their superior and inferior portions,
respectively, the lowest temperatures occur.
Water is almost incompressible, and expands
much less by heat than does the elastic air, con-
sequently the currents in the latter are far
more active and the cold in its higher regions
results chiefly from cooling by expansion of
the rising currents, whereas the cold at the
bottom of the sea is the result of the descent
of the denser water flowing from the poles.
The rate of decrease of temperature with in-
creasing depth in the water is faster than with
increasing height in the air and in both is most
rapid at the equator. There is a semi-diurnal
tide in the lower air like that on the surface of



4 THE CONQUEST OF THE AIR

the sea, but the irregular changes of pressure
amounting sometimes to one-fifteenth of the
whole atmospheric pressure, produce the vio-
lent circulation in storms.

Such, then, are some of the similarities and
differences between the superior and inferior
oceans, on the border-line of which man has
hitherto been content to live. While the seas
have been completely mastered by man, at least
superficially, the atmosphere offers to his in-
genuity a medium that is equally navigable
through a great thickness, and which domi-
nates seas and mountains and so unites the
nations. Obstacles to its use are the small sup-
porting power which it affords and the vio-
lent commotions to which it is subject. More-
over, while a ship, by utilizing the resistance
of the relatively stationary water on its side
and rudder can deviate from the wind, a bal-
loon resembles a submarine boat and if it pos-
sesses no motive power must drift with the cur-
rent in which it is wholly immersed. How-
ever, as will be shown later, by taking ad-
vantage of a superposed or underlying air cur-
rent blowing in an opposed direction, it may be
possible for such an aerial craft to return to its
starting point.



THE

EXPLORATION

OF THE

ATMOSPHERE



-14



ALTO^CU.




FIG. i. Comparative Altitudes.



THE OCEAN OF AIR 7

An idea of how far the ocean of air has been
explored is given in Fig. i, which represents
a vertical section of the atmosphere with the
barometric pressures at the left which corre-
spond to the successive heights marked on the
right. The right-hand half of the diagram in-
cludes the eastern hemisphere and the highest
mountains on the globe with the line of per-
manent snow and the greatest height to which
man has climbed. The observatories on the
Misti, in Peru, and on Mont Blanc, that had
self-recording instruments, as well as the
highest permanently inhabited place, are in-
dicated. As regards the free air we see the
relative levels reached by a kite and by man
in a balloon and, at the top of the dia-
gram, the height reached by ballons-sondes,
which carry only self-recording instru-
ments. The extreme height reached by such
a balloon is 18 miles, which is more than
twice as high as a human being can hope to at-
tain, for the atmospheric pressure there is but
a fraction of an inch of mercury, instead of 30
inches, which is the average density of the air
that we breathe at sea-level. It may be per-
ceived from the diagram that the pressure is
reduced, generally speaking, about one-half



8 THE CONQUEST OF THE AIR

for each three and a half miles of ascent, al-
though the intervals diminish progressively
upward. This rapid rarefaction makes it prac-
tically certain that the navigable portion of the
air lies below seven miles, since here the atmos-
pheric pressure becomes only a quarter of the
normal. This lower portion of the atmosphere,
which contains three-quarters of the whole
mass, is unfortunately the region of storms
and of the clouds which accompany them, for
only occasionally are the cirrus, or ice-clouds,
seen as high as nine miles. The winds which
blow around our centers of low barometric
pressure are replaced, above two or three miles,
by the nearly constant, but rapid planetary
circulation of the atmosphere, which, in tem-
perate latitudes, is from west to east.

As was remarked, a great deal of informa-
tion about the free air has been gathered by
sending into the air instruments attached to
kites and ballons-sondes, or sounding balloons.
The latter are small balloons, now commonly
made of sheet rubber, which carry barometers
and thermometers especially designed to record
very low pressures and temperatures, graphi-
cally and continuously. After the balloons
reach their highest altitude they fall to the



THE OCEAN OF AIR 9

ground, where they are generally found and
returned to the sender, and from the auto-
matic records of their instruments the heights
reached from moment to moment can be cal-
culated, together with the temperature pre-
vailing at these heights. Instruments lifted by
kites show in more detail the conditions
within two or three miles of the ground, 'and
have the advantage of furnishing the data with
greater certainty and nearly vertically over the
station on the ground. The humidity can thus
be measured and also the velocity of the wind,
because the kite may remain stationary in any
current at the will of the operator. Clouds,
which float at different heights in the atmos-
phere, also afford a method of determining the
direction and velocity of the air-currents. If
the average heights of the different classes of
clouds have been computed from angular meas-
urements on a base-line, measurements of the
apparent motion of these clouds will enable
their true velocity, as well as their direction of
motion, to be obtained at any time with suffi-
cient accuracy. All these methods have been
employed by the staff of the Blue Hill Observa-
tory, obviating the necessity of ascending into
the air themselves, and the results which will



io THE CONQUEST OF THE AIR

be given typify the general conditions prevail-
ing over the United States. In order to obtain
a continuous series of observations at a fixed
height above sea-level, it is still necessary to
make them on mountains, but, since these




FIG. 2. Annual Isotherms above St. Louis.

form a part of the earth's crust, such observa-
tions, even when made on an isolated peak, do
not represent the conditions at an equal height
in the free air, because the mass of the moun-
tain influences the temperature and moisture



THE OCEAN OF AIR 11

of the surrounding air and modifies the air
currents which come in contact with it.

The temperature is of considerable impor-
tance to the aeronaut. It was said that, as we
rise in the atmosphere, the temperature de-
creases, and, as a matter of fact, this occurs
so rapidly that in an ascent of a few hundred
feet the change in temperature corresponds to
a displacement in latitude on the earth's sur-
face of several hundred miles. Fig. 2 shows
the height of the isotherms, or lines of equal
temperature, at each season, obtained from
the records of 62 ascensions of ballons-sondes
at St. Louis. In this and the following dia-
grams the heights are expressed in kilometers,
16 kilometers being equivalent to 10 miles.
The temperatures are given in Centigrade de-
grees, so that o C. is equivalent to 32 F.,
20 C. to 68 F., and minus 60 C. to 76 F.
below zero. The diagram shows that the line
of o C. nearly touches the ground at St. Louis
in the winter, but in midsummer rises 3,800
meters above it, the surface temperature being
more than 20 C. It will be noticed that the
curves of equal temperature preserve approxi-
mately the same form and distance apart,
though they are somewhat more crowded



12 THE CONQUEST OF THE AIR

above six kilometers, showing that the most
rapid decrease of temperature is here. In fact,
the rate of decrease nearly equals the adiabatic
change for dry air, namely, i C. per 100
meters, or i F. per 183 feet, which is the cool-
ing produced by the expansion of the air as it
ascends, without the passage of heat to or from
the air. Above 13 kilometers, however, the
decrease of temperature is generally trans-
formed into an increase of temperature with
increasing height, though the height of this
plane of inversion varies with the season. The
cause and thickness of this warm stratum is un-
known, but it was found to. persist in Europe at
29 kilometers, or 18 miles, and it appears com-
pletely to surround the globe, being highest
over the equator, and lowest in the arctic
regions. However, it is only relatively warm,
as the temperature is still some 70 F. below
zero. The observations in the United States
prove that in this warm stratum, between
about 13 and at least 17 kilometers, there
is nearly always a rise of temperature. For
instance, on October 8, 1907, the temperature
rose 9 C., between 14,500 and 16,000 meters.
Taking another example, on November 6,
1907, the minimum temperature of 52 C.



THE OCEAN OF AIR 13

was found at 9,700 meters, and increased
nearly 2 C. within the next 300 meters,
whereas on November 8, the minimum tem-
perature of 63 C. occurred at 14,250 meters
and rose 3 in the succeeding 1,130 meters,
showing a change in level of the warm stratum
of 4,550 meters within two days.

In the preceding diagram the seasonal
effect of temperature is evident up to 10 kilo-
meters, a height which has been attained by
aeronauts, although the period of greatest
warmth is retarded so that it here occurs in the
autumn, as evinced by the maximum height
of the isotherm of 50 C at that season.
While the upper isotherm of 60 C. repre-
sents the lowest average temperature at any
height, yet an extreme temperature of 70
C, or 110 F. below zero, was recorded in
January, 1905, at a height of 14,800 meters,
or about nine miles, this being one of the low-
est natural temperatures ever observed in the
air or on the earth, and even in the following
July, 59 C., or 75 F. below zero, was regis-
tered at a slightly lower altitude. While the
heights at which these temperatures were re-
corded probably can never be reached by hu-
man beings, yet, even at the altitudes to which



14 THE CONQUEST OF THE AIR

aeronauts do ascend, it is intensely cold
throughout the year, and this, combined with




FIG. 3. Diurnal Temperatures at Different Heights.

the rarefaction of the air, acts as a barrier to
the attainment of greater heights.

But as aerial navigation will be carried on
at comparatively low levels, it is necessary to
examine in more detail the conditions which
prevail in the lower mile or two of air. For
many years these have been observed with
kites at Blue Hill, and like the balloon obser-
vations, the results of their study by Mr. Clay-
ton, meteorologist at the Observatory, are pub-



THE OCEAN OF AIR 15

lished in its Annals, and only some of tnem
can be briefly stated here.

While it was seen that the seasonal and non-
periodic changes of temperature are felt even
at great heights, we shall find that this is not
true for the average hourly changes which are
exhibited in Fig. 3. Here the curves for three
levels are plotted for every two hours With
their values in Fahrenheit degrees on the left
and in Centigrade degrees on the right.
The curve for 15 meters elevation is for
a station on the ground and shows the
well-known diurnal range of temperature with
the maximum in the early afternoon and the
minimum in the early morning. The three
other curves were obtained in the free air with
the kite at 500, 1,000 and 1,500 meters (almost
a mile), respectively; the dotted lines for the
first two representing the results of a different
method of reducing the data. They all show
a diminished range of temperature from that
at the ground, and in the curves at the highest
levels the phases of the ground-curve are al-
most reversed, so that it is warmest at night
and coldest about noon. Curves plotted for
the relative humidity at these same heights
show them to be nearly the inverse of the tern-



16 THE CONQUEST OF THE AIR



perature curves, that is, the lower mile of air,
excepting the surface-stratum, is, relatively,



woo

3500

3000

2500

1000

1500

1000

500





Temp.



Rel.H



Tem|



Vind V



WinlVel.



FIG. 4. Vertical Gradients above Blue Hill.

warm and dry at night and cold and damp in
the daytime.

The average vertical gradients of these two
elements and also of wind velocity, up to a



THE OCEAN OF AIR 17

height of 4,000 meters, or two and a half miles,
are plotted in Fig. 4. Here the lines inclining
upwards to the right indicate increasing values
and lines leaning to the left decreasing values,
the dotted lines showing the nocturnal condi-
tions. The temperature in the daytime de-
creases with height in the manner described,
but at night is seen to increase up to the vicin-
ity of 500 meters above the ground, on account
of the nocturnal cooling of the soil by radiation
and the consequent chilling of the contiguous
air. The relative humidity increases in the
daytime up to about 1,000 meters, and then
falls to a minimum above the lower clouds at
the height of a mile and a half. At night, how-
ever, it is already dry a quarter of a mile above
the ground, because of the absence of ascend-
ing currents of air. It should be remembered
that all these are average conditions, for strata
are found at every height which differ
greatly in temperature and humidity from the
adjacent air, and are accompanied by abrupt
changes in the direction and velocity of the
wind.

Clouds constitute an obstacle to aerial navi-
gation. If the aeronaut is enveloped in a cloud,
or is between two strata which obscure both



18 THE CONQUEST OF THE AIR

the earth and the sun or stars, he cannot tell
where he is or whither he is going, and, more-
over, moisture and, in greater degree, rain or
snow overload his airship or disturb its
balance. A balloon may be destroyed in the
air by lightning and the up-rush of wind in
the cumulo-nimbus, or thunder-shower clouds
would jeopardize any airship caught in its
embrace. The heights of the typical clouds,
namely, nimbus, cumulus, alto-cumulus, cirro-
cumulus, cumulo-nimbus and cirrus, which
are much the same all over the world,
were shown in Fig. I. They tend to arrange
themselves in distinct levels, with a maximum
frequency between three-quarters of a mile
and a mile and a quarter, and in other zones
of frequency at regular intervals up to about
six miles. We may place at eight miles the
upper limit of the cirri form clouds, appearing
to us on the earth as filaments, or as a thin veil
through which the sun is faintly visible, but
which are recognized as floating ice-crystals
by aeronauts who have traversed them at a
height of five or six miles. Rain or snow may
fall from alto-nimbus, a uniform cloud-sheet
more than a mile above the ground, but
commonly comes from a ragged sheet of nim-



THE OCEAN OF AIR 19

bus about half a mile high. In summer rain
or hail also falls from cumulo-nimbus, whose
towering top often extends into the cirrus re-
gion, whereas the thickness of the ordinary
raincloud does not exceed two miles, and may
be traversed usually by a balloon. On emerg-
ing from the darkness of the cloud into the








FIG. 5. 'Sea of Clouds Seen from a Balloon.

bright sunshine which illumines the white
cloud-billows, we have the scene repre-
sented in Fig. 5, which was photographed by
the author, near London, at a height of 6,000
feet. The shadow of the balloon, surrounded
by an aureole, is seen upon the cloud in the
middle of the foreground. Since the average
height of the different classes of clouds is



20 THE CONQUEST OF THE AIR

known, the apparent motion of a particular
cloud when observed at the ground gives to the
aeronaut, wishing to start on a voyage, quite
accurate information about the direction and
speed of the air currents prevailing at that
height, and in this way clouds serve as a wind
gauge for the upper air.

Of all the meteorological elements the wind
is the one with which aeronauts and aviators
are most concerned. The relative change of
velocity with height is indicated in Fig. 4, in
which the rapid increase for a short distance
above the ground is conspicuous. At night
the acceleration in velocity is even more
marked, attaining its maximum at the height
of one-third of a mile. Higher up, in the day-
time, the velocity increases slowly but at night
decreases somewhat, except in winter, up to
about 1,000 meters, or two-thirds of a mile.
Above this height there is a steady increase
of wind velocity with height and the rate
of increase is greater above 2,500 meters,
or a mile and a half. Fig. 6 shows bi-hourly
wind velocities at Boston, 60 meters; Blue Hill,
200 meters; and in the free air at 500 and
1,000 meters. At Boston the wind velocity is
distinctly greatest in the afternoon and least



THE OCEAN OF AIR



21



at night. On Blue Hill the diurnal change is
small, but at 500 meters the period at the lower
station is reversed, since the minimum velocity
occurs in the afternoon and the maximum at
night, and at 1,000 meters there are indica-



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Online LibraryAbbott Lawrence RotchThe conquest of the air; or, The advent of aerial navigation → online text (page 1 of 8)