BALLOONS--NOTABLE ASCENTS AND RESULTS OBTAINED--CAPTIVE BALLOONS
In the first chapter the invention of the hot-air and the hydrogen
balloon was chronicled, and it was stated that on December 1, 1783,
Charles rose from Paris to a height of 9000 feet. Public interest in
France was greatly excited by this wonderful extension of the realm of
man, and numerous ascensions with _MontgolfiËres_ and _CharliËres_, as
the hot-air and hydrogen balloons were respectively called, took place
in Paris and the provinces. The uses of the balloon seemed
innumerable, and Lavoisier was instructed by the Academy of Sciences
to draw up a report on the value of the new discovery. After having
described in detail the ascensions which he had witnessed, the great
chemist stopped, appalled at the multitude of problems which the
balloon could solve. History has shown, however, that no commercial
application of the balloon was possible, and that aside from its
spectacular attractions, its chief use has been for scientific
observations.
The first persons in England who devoted themselves to aÎrial
navigation were foreigners. Two of them were Italians, the philosopher
Tiberius Cavallo, who already in 1782 had showed to a London assembly
that soap-bubbles filled with hydrogen will rise, and therefore had
almost anticipated the invention of the hydrogen balloon, and the
diplomatist Vincent Lunardi, who made some daring balloon ascents in
1784. But the honour of making the first scientific balloon voyage is
due to a Bostonian, Dr. John Jeffries. Dr. Jeffries graduated at
Harvard College in 1763 and then practised medicine in England, where
he became a loyalist, and during the Revolution was with the British
troops. In London he interested himself in aerostation, and, aided by
the Royal Society, ascended in a balloon because, he said, "I wished
to see the following points more clearly determined: first, the power
of ascending or descending at pleasure, while suspended and floating
in the air; secondly, the effect which oars or wings might be made to
produce towards the purpose and in directing the course of the
balloon; thirdly, the state and temperature of the atmosphere at
different heights from the earth; and fourthly, by observing the
varying course of the currents of air, or winds, at certain
elevations, to throw some new light on the theory of winds in
general." A French professional aeronaut named Blanchard had made
three ascents in France and one in England, and Dr. Jeffries paid one
hundred guineas to accompany Blanchard on his fifth ascent, which was
made from London November 30, 1784. He took with him a thermometer, a
barometer, a hygrometer, an electrometer, and a mariner's compass,
also several numbered bottles, filled with water and provided with
glass stoppers, which were to be emptied and corked up at different
heights in the atmosphere. It was arranged to record the observations
on ruled paper with a silver pen, because the doctor would not trust a
common pen or pencil as liable to accident. He also had a map of
England to determine the direction which the balloon took. Jeffries'
English sentiments are shown by this quotation from his narrative: "I
had provided a handsome British flag, invidiously represented the next
day in one of the public papers to have been the flag of the American
States." The barometer and thermometer were observed every few
minutes, and the hygrometer occasionally. The electrometer did not
change its indications. Samples of air were obtained and sent to the
Royal Society, but it does not appear that they were ever analyzed.
The balloon rose nearly two miles, and descended safely in Kent after
an hour and a half. Jeffries' observations compare favourably with
those made until recently; indeed, for nearly a century there was
little improvement in the apparatus. The decrease of temperature which
Jeffries found, viz. 1∞ for 360 feet rise, and the decreasing humidity
with height agree very well with later observations.
Jeffries and Blanchard undertook a more perilous voyage on January 7,
1785, from Dover across the Channel, landing in the province of
Artois, after, so runs the announcement, "we were suspended and
floating in the atmosphere two hours over the sea and forty-seven
minutes over the land of France." The voyagers were cordially
welcomed, and were entertained lavishly in Paris as being, Jeffries
says, "the first who passed across the sea from England into France by
the route of the air." No instruments but a barometer and a compass
were carried, and the only scientific result worthy of notice was that
the balloon seemed to lose buoyancy over the sea, due to what Jeffries
thought might be "the power of attraction over the water." The height
of the balloon was measured trigonometrically by French officers in
Calais, who found by angular measures, when the balloon was midway
across the Channel, that its height was 4500 feet. Jeffries' voyages
have been described somewhat at length because the first scientific
balloon voyage is generally attributed to the Belgian physicist,
Robertson, who ascended from Hamburg in 1803 to the improbable height
of 24,000 feet. Robertson made his third ascent the next year from St.
Petersburg, accompanied by the Academician Sacharoff. This was a
scientific voyage, instituted at the request of the Russian Academy,
to ascertain the physical state of the atmosphere and the component
parts of it at different heights, also the difference between the
results of vertical ascents and the observations of Deluc, De
Saussure, von Humboldt and others on mountains, which it was rightly
concluded could not be so free from terrestrial influences as those
made in the open air. Among the experiments which the Academy proposed
were the following: change of rate of evaporation of fluids, decrease
or increase in the magnetic force, inclination of the magnetic needle,
increase of heat of the solar rays, fainter colours in the spectrum,
influence of rarefaction of the air on the human body, as well as some
other chemical and philosophical experiments. A height of about two
miles was reached, and many interesting observations were made, but
since the instruments were not easily used in the basket of the
balloon, the results were unsatisfactory and required repetition to be
conclusive.
The Academy of Sciences of Paris now took up the investigation with
the special object of proving whether the magnetic force decreased as
Robertson in a balloon and De Saussure in the Alps had supposed. Two
young physicists, Biot and Gay-Lussac, were chosen to carry out the
investigations. They ascended from Paris on August 24, 1804, provided
with all necessary instruments, but the balloon was too small to rise
higher than 13,000 feet. Gay-Lussac ascended alone to a height of
23,000 feet on September 16, 1804, in a balloon filled with hydrogen.
His observations confirmed those which he had made with Biot, that
there was no change in the magnetic force, and from samples of air
collected he proved that the chemical constitution of the air is
invariable. His observations of temperature seemed to confirm the
theory of a decline of temperature of 1∞ in 300 feet of elevation. The
air was found to be very dry, and Gay-Lussac noticed that at the
highest altitude the clouds were still far above him.
Passing over several notable ascents in other countries, it was not
until 1850 that scientific ballooning was begun again in the land
where the balloon originated. Then MM. Barral and Bixio made two
ascents from Paris in rainy weather to the heights of 19,000 and
23,000 feet respectively, although they had expected to attain twice
these altitudes. Their most interesting observations were the great
thickness of the cloud mass, which in one case amounted to 15,000
feet, and the sudden fall of temperature in it from +15∞ to -39∞. Some
curious optical phenomena were connected with the floating ice
crystals, and although the light of the sky was found to be strongly
polarized, the light reflected from the clouds was not polarized.
The field of operations was now transferred to England, where, under
the auspices of the British Association, four ascents were made by
John Welsh of the Kew Observatory in the great _Nassau_ balloon
managed by Green, the veteran aeronaut. The special object of these
investigations, like those in France, was the determination of the
temperature and hygrometric condition of the air at different
elevations. Besides this, samples of air at different heights were
collected for analysis and the light reflected from clouds was
examined for polarization. Recognizing that on account of the calm
prevailing in the car of the balloon and the great solar radiation,
the readings of the thermometer would be affected, Welsh enclosed the
thermometers in polished tubes through which air was forced by
bellows. This was the first aspirated thermometer, which alone gives
the true temperature of the air with the conditions prevailing in a
balloon. The instrument fell into oblivion until a few years ago, and
to this fact is due the fictitious temperatures generally obtained by
aeronauts. Welsh reached heights of from 12,500 to 23,000 feet, and
his observations showed that the temperature of the air decreased
uniformly with height until at a certain elevation, varying on
different days, the decrease is arrested, and for a space of 2000 or
3000 feet the temperature remains nearly constant, or even increases
slightly; the regular diminution being afterwards resumed and
generally maintained at a less rapid rate than in the lower air, and
commencing from a higher temperature than would have existed but for
the interruption. The variation of the decrease with the seasons was
also demonstrated. The humidity did not change much with height, and
it was nowhere very dry. Finally, the light of the clouds was proved
not to be polarized, and the permanent composition of the atmosphere
was confirmed.
In 1861 another grant of money was made by the British Association for
balloon experiments to be performed, under the direction of a
Committee, by Mr. James Glaisher, then engaged in geodetic and
meteorological work in England. Between 1862 and 1868 Glaisher,
accompanied by the aeronaut Coxwell, made thirty ascents. They
attained three times a height exceeding 23,000 feet, and once more
than 29,000 feet, when they believed that the balloon rose to 37,000
feet. The primary objects of Glaisher's experiments were as follows:
determination of the temperature of the air and its hygrometrical
conditions up to five miles, comparisons of an aneroid barometer with
a mercurial one, determination of the electrical state of the air and
of its oxygenic state by means of ozone papers, time of vibration of a
magnet at different distances from the earth. Secondary objects of
study were the composition of the air, the form and thickness of
clouds, the atmospheric currents, acoustical phenomena, etc. In order
to obtain many observations frequent ascents were necessary, as the
insular position of England precluded long voyages. During 1869
ascents in a captive balloon up to 1700 feet supplemented the
employment of the free balloon, which from its rapid rise and fall
made observations in it near the earth impossible. Glaisher was a good
observer; his instruments were excellent, and had been previously
tested, but their exposure in the basket of the balloon was bad, and
although the thermometer was provided with an aspirator similar to
Welsh's, Glaisher, noticing that the readings agreed with those of a
freely exposed thermometer, hastily concluded that the use of the
aspirator was unnecessary, and so discarded it.
Until quite recently Glaisher's results were accepted as representing
the conditions of the free air up to the greatest height which it was
possible to reach. These results showed that the temperature did not
fall uniformly with height, but that it fell most rapidly near the
earth and much less rapidly at great heights. In cloudy weather up to
the height of a mile the mean decrease of temperature in the day-time
differed little from the theory of 1∞ per 300 feet, but in clear or
partly clear weather the decrease was more rapid, commencing with 1∞
for 160 feet near the ground and diminishing to 1∞ for 1000 feet at an
elevation exceeding six miles. The observations in the captive balloon
up to a third of a mile indicated a daily range in the vertical
decrease of temperature. The observations of relative humidity agreed
with Welsh's in showing a slight increase up to about half-a-mile,
then a decrease up to above five miles, where there seemed to be an
almost entire absence of water. The other observations were
inconclusive, except that the time of vibration of a magnet was found
to be somewhat longer than on the earth, which was contrary to
Gay-Lussac's experience. The most remarkable of Glaisher's ascents was
made from Wolverhampton on September 5, 1862, when in less than one
hour he had passed the altitude of five miles, exceeding the greatest
height hitherto reached. To quote from Glaisher's narrative: "Up to
this time I had taken observations with comfort and experienced no
difficulty in breathing, whilst Mr. Coxwell, in consequence of the
exertion he had to make, had breathed with difficulty for some time.
Having discharged sand, we ascended still higher; the aspirator became
troublesome to work, and I also found a difficulty in seeing
clearly.... About 1 hour 52 min., or later, I read the dry-bulb
thermometer as minus 5∞; after this I could not see the column of
mercury in the wet-bulb thermometer, nor the hands of the watch, nor
the fine divisions of any instrument. I asked Mr. Coxwell to help me
to read the instruments. In consequence, however, of the rotatory
motion of the balloon, which had continued without ceasing since
leaving the earth, the valve-line had become entangled, and he had to
leave the car and mount into the ring to readjust it. I then looked at
the barometer, and found its reading to be 9-3/4 inches, still
decreasing fast, and implying a height exceeding 29,000 feet. Shortly
after, I laid my arm upon the table, possessed of its full vigour, but
on being desirous of using it, I found it powerless.... Trying to move
the other arm, I found it powerless also. Then I tried to shake myself
and succeeded, but I seemed to have no limbs.... I dimly saw Mr.
Coxwell, and endeavoured to speak, but could not. In an instant
intense darkness overcame me, so that the optic nerve lost power
suddenly, but I was still conscious, with as active a brain as at the
present moment whilst writing this. I thought I had been seized with
asphyxia, and believed I should experience nothing more, as death
would come unless we speedily descended; other thoughts were entering
my mind, when I suddenly became unconscious.... I cannot tell anything
of the sense of hearing, as no sound reaches the air to break the
perfect stillness and silence of the regions between six and seven
miles above the earth. My last observation was made at 1 hour 54 min.,
above 29,000 feet.... Whilst powerless I heard the words,
'temperature' and 'observation,' and I knew Mr. Coxwell was in the car
speaking to and endeavouring to rouse me.... I then heard him speak
more emphatically, but could not see, speak, or move. I heard him
again say, 'Do try; now do!' Then the instruments became dimly
visible, then Mr. Coxwell, and very shortly I saw clearly.... Mr.
Coxwell told me that while in the ring he felt it piercingly cold,
that hoarfrost was all round the neck of the balloon, and that on
attempting to leave the ring he found his hands frozen. He had,
therefore, to place his arms on the ring and drop down.... He wished
to approach me, but could not; and when he felt insensibility coming
over him too, he became anxious to open the valve. But in consequence
of having lost the use of his hands he could not do this; ultimately
he succeeded, by seizing the cord with his teeth, and dipping his head
two or three times, until the balloon took a decided turn downwards.
No inconvenience followed my insensibility; and when we dropped, it
was in a country where no conveyance of any kind could be obtained, so
I had to walk between seven and eight miles.... I have already said
that my last observation was made at a height of 29,000 feet; at this
time (1 hour 54 min.) we were ascending at the rate of 1000 feet per
minute; and when I resumed observations we were descending at the rate
of 2000 feet per minute. These two positions must be connected, taking
into account the interval of time between, viz. 13 minutes, and on
these considerations the balloon must have attained the altitude of
36,000 or 37,000 feet. Again, a very delicate minimum thermometer read
minus 11∞.9, and this would give a height of 37,000 feet. Mr. Coxwell,
on coming from the ring, noticed that the centre of the aneroid
barometer, its blue hand, and a rope attached to the car were all in
the same straight line, and this gave a reading of seven inches and
leads to the same result. Therefore, these independent means all lead
to about the same elevation, viz. fully seven miles."
Mr. Glaisher's circumstantial evidence of the height he reached has
been assailed lately, partly from his assumption that the velocity of
the balloon while rising and falling during the thirteen minutes was
uniform, but principally from the supposition that men could have
survived in that region of death, without at least artificial means of
respiration. While it is certain that Berson's observations, which are
described later, were made at a greater height than Glaisher's, yet
all credit must be given to this Nestor of aeronautical and
meteorological science in Great Britain, who is still living at the
advanced age of ninety.
The example of Glaisher was not followed in England, but it stimulated
interest in the balloon again in France, where MM. Flammarion, de
Fonvielle, and Tissandier have made many ascents for scientific
purposes, and have presented the results in a popular form to the
public. Photography in a balloon is generally a failure on account of
the intense reflection from the upper cloud surfaces and the haze
which masks the earth. Consequently, for scenic effects we must rely
upon sketches, of which those in that interesting, but now rather rare
book, _Travels in the Air_, may be referred to. The high atmosphere is
often filled with fine ice crystals which, though invisible from
below, occasion curious optical phenomena, and some of these have
been sketched by M. Albert Tissandier, who has the advantage of being
an artist as well as an aeronaut.
Of the many narratives of balloon voyages, one of the most thrilling
is the tragedy of the _Zenith_. In 1875, through the co-operation of
the French Academy of Sciences and other scientific bodies, it was
arranged to make two voyages, one of long duration, the other to a
great height, in the balloon _Zenith_. The long voyage from Paris to
Bordeaux was successfully accomplished in twenty-four hours, and on
April 15 the _Zenith_ again rose from Paris, carrying MM. Gaston
Tissandier and CrocÈ-Spinelli, with Sivel as aeronaut. By the advice
of M. Paul Bert, the distinguished physiologist, three small balloons
of oxygen were provided to assist respiration. The scientific
apparatus was as follows: a pump was arranged to draw air through
tubes filled with potash in which to store the carbonic acid at
different heights in the atmosphere, in order that analysis might
determine if its proportion diminished at great heights; a
spectroscope was employed to examine the line of water-vapour in the
atmosphere, and two aneroid barometers were provided, one giving the
pressure corresponding to heights up to 13,000 feet, the other the
pressure between 13,000 and 30,000 feet. There were also two
barometric tubes registering the lowest pressure, as well as
thermometers and other scientific instruments. At 15,000 feet the
voyagers began to breathe oxygen, which had been used beneficially by
Sivel and CrocÈ-Spinelli in a high ascent the previous year. At 24,000
feet Tissandier wrote in his notes: "My hands are freezing. I am well.
We are all right. Haze on horizon with small rounded cirrus. We are
rising. CrocÈ pants. We breathe oxygen. Sivel shuts his eyes, CrocÈ
does the same." Five minutes later: "Sivel throws out ballast,
temperature -11∞ Cent., barometer 300 millimeters." After this,
Tissandier became so weak that he could not turn his head to look at
his companions. He tried to seize the oxygen tube, but was unable to
move his arms. His mind was clear, and he saw the barometer sink below
280 millimeters, indicating a height of 27,000 feet. Then he fainted.
After a half-hour of unconsciousness he revived and wrote: "We are
falling, temperature -8∞, barometer 315 millimeters. I discharge
ballast. CrocÈ and Sivel unconscious in bottom of basket. We fall
rapidly." Again he fell into a stupor, from which he was roused by
CrocÈ shaking his arm, saying, "Throw out ballast!" which he did,
together with the pump, wraps, etc. What happened after this is
unknown, but probably the balloon, thus lightened and the gas in it
being warm, rose again nearly as high as before. When Tissandier came
to his senses the balloon was falling with frightful speed, and in the
bottom of the basket, which was oscillating violently from side to
side, were crouched his two companions with black faces and bloody
mouths. The shock of striking the ground was terrific, but the anchor
held, and the balloon soon emptied. From the barometric data it
appears probable that the _Zenith_ attained twice a height of about
28,000 feet, and that asphyxiation from the long deprivation of
sufficient oxygen killed the two companions of Tissandier and nearly
proved fatal to him.
This disaster discouraged further attempts to reach high altitudes,
and with the exception of the ascent to 23,000 feet in France by MM.
Jovis and Mallet, no more were made until the past decade. The results
of the meteorological observations were seen to be strangely
discordant; for example, the temperature of 40∞ below zero, observed
by Barral and Bixio at a height of 23,000 feet, and 80∞ above zero,
noted by the American aeronaut Wise, at 6000 feet. The prophecy "that
the balloon-basket would be the cradle of the young science of
meteorology" seemed unlikely to be realized, but, nevertheless,
observations in balloons continued to be made in France, Italy, and
Russia. In the United States a series of balloon ascents was
conducted by the Signal Service, which then included the Weather
Bureau, and the height of 15,500 feet reached by Professor Hazen in
1887 is probably the greatest at which observations in the free air
have been made in America.
The difficulty of obtaining the true temperature of the air from a
balloon is great, and without special precautions the observations
give the conditions of the free air even less well than do
observations on mountain summits. During a rapid ascent the air is
carried up in the balloon basket like water in a well-bucket, and
since the balloon drifts with the wind it is relatively in a calm, so
that there is no circulation of air; the thermometers, even when
screened from direct sunshine, are affected by radiation from the
heated gas-bag above, and moreover they are not sufficiently sensitive
to follow the changing temperature of the air strata so quickly
traversed by the balloon. The aneroid barometer, from which the height
of the balloon is calculated, cannot respond to rapid changes of
pressure; consequently there is a double source of error in
determining the height at which the temperature is measured.
Ordinarily, the temperature of the air may be obtained quite
accurately by slinging in a circle a thermometer attached to a cord,
even though this is done in sunshine. During two balloon ascents by
the writer, a sling thermometer was found in extreme cases to read 14∞
lower than was recorded by automatic instruments, hung in their usual
position from the ring of the balloon. The sling thermometer, however,
is influenced by intense insolation, and moreover cannot be swung far
enough outside the basket of a balloon to insure good results. The
standard instrument for obtaining the temperature of the air under all
conditions, adopted for international use in 1898, is a modification
of that used by Welsh forty-five years before. This instrument, which
is the invention of Dr. Assmann of Berlin, is called the aspiration
thermometer, and is designed to prevent the casing surrounding the
thermometer from being heated by insolation or conduction, and to
insure a flow of air past the thermometer bulbs.
[Illustration: FIG. 3.--German Balloon equipped for
Meteorological Observations.]
The reorganization of balloon observations was accomplished by the
German Society for the Promotion of AÎrial Navigation, which has been
assisted by the Prussian Meteorological Institute, and by officers of
the German Army Balloon Corps. The German Emperor takes a personal
interest in the work, and has aided it by the gift of a considerable
sum of money. The first voyage under the direction of the Society was
made in 1888, and many notable ones followed. In 1891, through the
courtesy of the president, Dr. Assmann, the writer made an ascent
from Berlin in a balloon equipped for accurate observations, with the
special purpose of comparing the sling with the aspiration
thermometer. The car of the balloon is shown in Fig. 3. A companion
was the now famous Dr. Berson, who then made his second ascent, but
who has now become an expert aeronaut by reason of more than fifty
ascensions, some of them to great heights. On December 4, 1894, he
ascended alone from Stassfurt, Prussia, in the _Phoenix_, to
probably the greatest height ever reached by man, at least in a
conscious state. By breathing oxygen he was able to keep his senses
and to read the barometer at 9∑1 inches, indicating approximately an
altitude of 30,000 feet, and the aspirated thermometer at 54∞ below
zero. An ordinary thermometer read 11∞ below zero in the sun, showing
its heat was much diminished in consequence of the haze that prevailed
even at this enormous height. The cirriform clouds which surrounded
the balloon were found to have the structure of snow-flakes rather
than that of ice-crystals. The chief result of this record-breaking
ascent was the extraordinarily low temperatures recorded at great
heights, as compared with those observed by Glaisher, Tissandier, and
others. An inversion of temperature--that is an increase of
temperature with height--prevailed up to a mile, but above that the
temperature fell at a rapid and accelerated rate which approached the
adiabatic fall above 26,000 feet. The wind, which was almost calm at
the earth's surface, increased to a gale in the high atmosphere, and
carried the balloon along at an average speed of thirty-six miles an
hour. Wishing to demonstrate conclusively whether the insular position
of England influenced the temperature of the high atmosphere, as had
been suggested, Dr. Berson determined to execute a high ascension in
England during the prevalence of a barometric maximum in summer, when
the air column would be abnormally warmed and the upper isothermal
surfaces elevated. An opportunity was afforded Berson to follow in
Glaisher's footsteps on September 14, 1898, when abnormal heat
prevailed in Europe. Berson, with the aeronaut Spencer, in the balloon
_Excelsior_, rose from the Crystal Palace in London to the height of
27,300 feet, where he observed a temperature of -29∞. The oxygen
inhaled prevented harmful physiological effects except for the
discomfort caused by the enormous reduction of temperature from 80∞ at
the ground only thirty-five minutes before. The temperature decreased
rapidly at first, then moderately up to three miles, and above that it
fell almost at the adiabatic rate. Even in this hot summer maximum of
pressure and notwithstanding the maritime climate and south-westerly
currents, a temperature about 29∞ below zero reigned at 27,000 feet,
being only a few degrees warmer than Berson had observed in winter at
the same height above Germany. Yet Glaisher, in all his ascents, two
of which exceeded 26,000 feet, never recorded a temperature of less
than 5∞ below zero. These relatively high temperatures, obtained also
by Welsh, Tissandier, and Gay-Lussac, must be attributed to the
insufficient protection of the thermometers against insolation, to the
proximity of the instruments to the heated basket and its occupants,
and lastly, to the sluggishness of the thermometers themselves, from
lack of ventilation, during the rapid passage through air-strata of
different temperatures. Plate VI. indicates the change of temperature
with height observed during the four highest balloon ascents in Europe
and in the United States. Dots indicate the observations while
ascending, and crosses the observations while descending; these are
connected by full and broken lines respectively, an inclination upward
to the left showing a decrease of temperature with height and _vice
vers‚_. The adiabatic lines, representing a fall of temperature of 1∞
Fahrenheit per 183 feet of ascent, serve for comparison.
[Illustration: PLATE VI.--Temperatures observed in Four High
Balloon Ascents.]
This account of notable balloon ascents should not be closed without
mentioning the most daring and unique of all, the voyage of Mr. S. A.
AndrÈe towards the north pole in 1897. Although his was a voyage of
geographical discovery, and not one for the exploration of the air,
yet meteorological and other observations were to be made, and AndrÈe
had familiarized himself with the instruments and the management of a
balloon during several voyages in Sweden. The success of the polar
voyage depended primarily upon the prevalence of southerly winds, and
the ability of the balloon to keep afloat long enough to profit by
them, even should they be light and variable at times. Therefore the
impermeability of the balloon to hydrogen gas was of vital
importance, and it was the conviction that the _Eagle_, of 140,000
cubic feet, was neither sufficiently large nor staunch to sustain
itself for thirty days, the time which might be required to reach
Behring Straits, that led Dr. Nils Ekholm, the meteorologist and
physicist, to withdraw from the expedition. Unfortunately, his fears
seem to have been well founded, and it is probable that we must now
abandon hope of the safety of the brave AndrÈe and his two companions.
A less perilous voyage northward across the Alps was attempted in 1898
by Professor Heim, the Swiss geologist, and two associates, conducted
by the Italian aeronaut, Spelterini. With an automatic photographic
camera, similar to one described in the next chapter, it was hoped to
get views of the high Alps from above, which would be alike valuable
for geologic and topographic study. Extensive meteorological
observations were made in connection with the sixth international
balloon ascent, but only the Jura was crossed, at an altitude of
13,000 feet, because the balloon travelled in a north-westerly
direction, instead of north-east as was expected.
Many years ago Wise and Donaldson, the American aeronauts, proposed to
cross the Atlantic Ocean in a balloon. The difficulties which present
themselves in such an undertaking are purely technical, and given a
balloon which loses its gas so slowly that its buoyancy can be
maintained for several days, there seems to be no reason why such a
balloon, at a height of four or five miles, could not pass from San
Francisco to New York, or from the United States to Europe, since the
motion of the upper clouds proves that the high atmosphere moves
almost constantly with great velocity from the west to the east. The
dirigible balloon has not been realized except in nearly calm weather,
but the aeronaut can often reverse his direction by ascending or
descending into a contrary wind to that in which he has been
travelling. Frequently no clouds separate these opposing currents,
which become apparent only when a balloon enters them.
It has been mentioned that in 1869 Glaisher made observations in a
captive balloon in England up to the height of 1700 feet in order to
study the conditions of the air within this distance of the earth,
which could not be done in a free and rapidly moving balloon. Although
captive balloons are frequently used in the European cities to lift
people who wish to enjoy the view from a height of 500 or 1000 feet,
they appear to have been little used by scientific observers since the
time of Glaisher. In 1890-91 the aeronautical society at Berlin
employed a captive balloon in connection with the observations in free
balloons which have been described. This captive balloon had a
capacity of only 5000 cubic feet, but it sufficed to lift an apparatus
weighing sixteen pounds, designed by Dr. Assmann to record atmospheric
pressure, as well as the temperature and relative humidity of the air.
The balloon, attached to a cable 2600 feet long, was drawn down by a
steam engine. It was possible in this way to have simultaneous
observations at three levels, viz. near the ground, in the free air at
a height of about half-a-mile, and at the highest level attained by a
free balloon. But the captive balloon is often at a disadvantage, for
the wind drives it down, and although the meteorograph mentioned had
ingenious devices to neutralize the violent shocks caused by this and
by the rebound of the balloon after the gust of wind, yet these
impaired the automatic record. The height to which the balloon rose
was so much diminished by the wind that instead of 2600 feet, which
the balloon attained in calm weather when the cable was vertical, the
average height of the twenty-four ascents was but half this, and in
very windy weather the balloon could not rise at all.
[Illustration: FIG. 4.--German Kite-balloon.]
To obviate these difficulties, a few years ago there was invented by
two officers of the German army, Lieutenants von Siegsfeld and von
Parseval, a captive balloon capable of resisting strong winds, called,
from its action as a kite, the _Drachen-Ballon_ or kite-balloon, and
which at the present time is being successfully used in the German
Army and Navy for reconnoitring in all kinds of weather. A smaller
kite-balloon, of 7700 cubic feet capacity, filled either with
hydrogen or with illuminating gas, was first used to lift
meteorological instruments at Strassburg in 1898, where it remained at
a height of several hundred feet during twenty-four hours. As is seen
from Fig. 4, the balloon is cylindrical, with hemispherical ends, and
is attached to its cable like a kite, so that the wind acts to lift
and not to depress it. The cylinder is divided by a diaphragm near its
lower end into two chambers, the upper and larger one being filled
with gas, while the lower chamber, by means of a valve opening
inwards, receives the pressure of the wind which presses against the
diaphragm, and preserves the sausage-like form of the balloon in spite
of leakage of gas. Another wind-bag encircling the bottom of the
air-chamber serves as a rudder, and lateral fins or wings give
stability to the balloon about its longer axis. The instruments are
placed in a basket hung far below the balloon. In cases where there is
little or no wind at the ground, captive balloons can render valuable
service for meteorological observations, but in all other cases kites
are preferable. The reasons for this assertion will be given when we
consider kites.
From what has been said it will be perceived how much the Germans did
to advance scientific ballooning, yet their constant rivals, the
French, found a way to surpass them in the exploration of the
atmosphere. For several years the struggle for supremacy in the
attainment of the greatest heights was keen between the scientific men
of both countries, but a truce was declared at Paris in 1896, and
since then both nations have worked together harmoniously. The
friendly meeting of French and German physicists at Strassburg in 1898
to agree upon the details of co-operation, typified the union of
nations through science, and while it is true that the atmosphere has
no boundaries and cannot be pre-empted, let us hope that the common
aims of science will ultimately obliterate even political boundaries.