THE BALLOON-HOAX
[Astounding News by Express, via Norfolk!—The Atlantic
crossed in Three Days! Signal Triumph of Mr. Monck Mason's Flying
Machine!—Arrival at Sullivan's Island, near Charlestown, S.C., of
Mr. Mason, Mr. Robert Holland, Mr. Henson, Mr. Harrison Ainsworth,
and four others, in the Steering Balloon, "Victoria," after a passage
of Seventy-five Hours from Land to Land! Full Particulars of the
Voyage!
The subjoined jeu d'esprit with the preceding heading in
magnificent capitals, well interspersed with notes of admiration, was
originally published, as matter of fact, in the "New York Sun," a
daily newspaper, and therein fully subserved the purpose of creating
indigestible aliment for the quidnuncs during the few hours
intervening between a couple of the Charleston mails. The rush for
the "sole paper which had the news," was something beyond even the
prodigious; and, in fact, if (as some assert) the "Victoria" did
not absolutely accomplish the voyage recorded, it will be difficult
to assign a reason why she should not have accomplished it.]
THE great problem is at length solved! The air, as well as the earth
and the ocean, has been subdued by science, and will become a common and
convenient highway for mankind.
The Atlantic has been actually crossed
in a Balloon! and this too without difficulty—without any great
apparent danger—with thorough control of the machine—and in the
inconceivably brief period of seventy-five hours from shore to shore!
By the energy of an agent at Charleston, S.C., we are enabled to be
the first to furnish the public with a detailed account of this most
extraordinary voyage, which was performed between Saturday, the 6th
instant, at 11, A.M., and 2, P.M., on Tuesday, the 9th instant, by Sir
Everard Bringhurst; Mr. Osborne, a nephew of Lord Bentinck's; Mr. Monck
Mason and Mr. Robert Holland, the well-known æronauts; Mr. Harrison
Ainsworth, author of "Jack Sheppard," &c.; and Mr. Henson, the
projector of the late unsuccessful flying machine—with two seamen from
Woolwich—in all, eight persons. The particulars furnished below may be
relied on as authentic and accurate in every respect, as, with a slight
exception, they are copied
verbatim from the joint diaries of Mr.
Monck Mason and Mr. Harrison Ainsworth, to whose politeness our agent is
also indebted for much verbal information respecting the balloon itself,
its construction, and other matters of interest. The only alteration in
the MS. received, has been made for the purpose of throwing the hurried
account of our agent, Mr. Forsyth, into a connected and intelligible
form.
"THE BALLOON.
"Two very decided failures, of late—those of Mr. Henson and Sir George
Cayley—had much weakened the public interest in the subject of aerial
navigation. Mr. Henson's scheme (which at first was considered very
feasible even by men of science,) was founded upon the principle of an
inclined plane, started from an eminence by an extrinsic force, applied
and continued by the revolution of impinging vanes, in form and number
resembling the vanes of a windmill. But, in all the experiments made
with models at the Adelaide Gallery, it was found that the operation of
these fans not only did not propel the machine, but actually impeded
its flight. The only propelling force it ever exhibited, was the mere
impetus acquired from the descent of the inclined plane; and this
impetus carried the machine farther when the vanes were at rest, than
when they were in motion—a fact which sufficiently demonstrates their
inutility; and in the absence of the propelling, which was also the
sustaining power, the whole fabric would necessarily descend.
This consideration led Sir George Cayley to think only of adapting
a propeller to some machine having of itself an independent power of
support—in a word, to a balloon; the idea, however, being novel,
or original, with Sir George, only so far as regards the mode of its
application to practice. He exhibited a model of his invention at the
Polytechnic Institution. The propelling principle, or power, was here,
also, applied to interrupted surfaces, or vanes, put in revolution.
These vanes were four in number, but were found entirely ineffectual in
moving the balloon, or in aiding its ascending power. The whole project
was thus a complete failure.
"It was at this juncture that Mr. Monck Mason (whose voyage from Dover
to Weilburg in the balloon, "Nassau," occasioned so much excitement in
1837,) conceived the idea of employing the principle of the Archimedean
screw for the purpose of propulsion through the air—rightly
attributing the failure of Mr. Henson's scheme, and of Sir George
Cayley's, to the interruption of surface in the independent vanes.
He made the first public experiment at Willis's Rooms, but afterward
removed his model to the Adelaide Gallery.
"Like Sir George Cayley's balloon, his own was an ellipsoid. Its
length was thirteen feet six inches—height, six feet eight inches. It
contained about three hundred and twenty cubic feet of gas, which, if
pure hydrogen, would support twenty-one pounds upon its first inflation,
before the gas has time to deteriorate or escape. The weight of the
whole machine and apparatus was seventeen pounds—leaving about four
pounds to spare. Beneath the centre of the balloon, was a frame of light
wood, about nine feet long, and rigged on to the balloon itself with
a network in the customary manner. From this framework was suspended a
wicker basket or car.
"The screw consists of an axis of hollow brass tube, eighteen inches in
length, through which, upon a semi-spiral inclined at fifteen degrees,
pass a series of steel wire radii, two feet long, and thus projecting a
foot on either side. These radii are connected at the outer extremities
by two bands of flattened wire—the whole in this manner forming the
framework of the screw, which is completed by a covering of oiled silk
cut into gores, and tightened so as to present a tolerably uniform
surface. At each end of its axis this screw is supported by pillars of
hollow brass tube descending from the hoop. In the lower ends of these
tubes are holes in which the pivots of the axis revolve. From the end
of the axis which is next the car, proceeds a shaft of steel, connecting
the screw with the pinion of a piece of spring machinery fixed in the
car. By the operation of this spring, the screw is made to revolve with
great rapidity, communicating a progressive motion to the whole. By
means of the rudder, the machine was readily turned in any direction.
The spring was of great power, compared with its dimensions, being
capable of raising forty-five pounds upon a barrel of four inches
diameter, after the first turn, and gradually increasing as it was wound
up. It weighed, altogether, eight pounds six ounces. The rudder was
a light frame of cane covered with silk, shaped somewhat like a
battle-door, and was about three feet long, and at the widest, one foot.
Its weight was about two ounces. It could be turned
flat, and directed
upwards or downwards, as well as to the right or left; and thus enabled
the æronaut to transfer the resistance of the air which in an inclined
position it must generate in its passage, to any side upon which he
might desire to act; thus determining the balloon in the opposite
direction.
"This model (which, through want of time, we have necessarily described
in an imperfect manner,) was put in action at the Adelaide Gallery,
where it accomplished a velocity of five miles per hour; although,
strange to say, it excited very little interest in comparison with the
previous complex machine of Mr. Henson—so resolute is the world
to despise anything which carries with it an air of simplicity. To
accomplish the great desideratum of ærial navigation, it was very
generally supposed that some exceedingly complicated application must be
made of some unusually profound principle in dynamics.
"So well satisfied, however, was Mr. Mason of the ultimate success of
his invention, that he determined to construct immediately, if possible,
a balloon of sufficient capacity to test the question by a voyage of
some extent—the original design being to cross the British Channel, as
before, in the Nassau balloon. To carry out his views, he solicited and
obtained the patronage of Sir Everard Bringhurst and Mr. Osborne, two
gentlemen well known for scientific acquirement, and especially for the
interest they have exhibited in the progress of ærostation. The project,
at the desire of Mr. Osborne, was kept a profound secret from the
public—the only persons entrusted with the design being those actually
engaged in the construction of the machine, which was built (under the
superintendence of Mr. Mason, Mr. Holland, Sir Everard Bringhurst, and
Mr. Osborne,) at the seat of the latter gentleman near Penstruthal, in
Wales. Mr. Henson, accompanied by his friend Mr. Ainsworth, was admitted
to a private view of the balloon, on Saturday last—when the two
gentlemen made final arrangements to be included in the adventure. We
are not informed for what reason the two seamen were also included in
the party—but, in the course of a day or two, we shall put our readers
in possession of the minutest particulars respecting this extraordinary
voyage.
"The balloon is composed of silk, varnished with the liquid gum
caoutchouc. It is of vast dimensions, containing more than 40,000 cubic
feet of gas; but as coal gas was employed in place of the more expensive
and inconvenient hydrogen, the supporting power of the machine, when
fully inflated, and immediately after inflation, is not more than about
2500 pounds. The coal gas is not only much less costly, but is easily
procured and managed.
"For its introduction into common use for purposes of aerostation, we
are indebted to Mr. Charles Green. Up to his discovery, the process of
inflation was not only exceedingly expensive, but uncertain. Two, and
even three days, have frequently been wasted in futile attempts to
procure a sufficiency of hydrogen to fill a balloon, from which it
had great tendency to escape, owing to its extreme subtlety, and its
affinity for the surrounding atmosphere. In a balloon sufficiently
perfect to retain its contents of coal-gas unaltered, in quantity or
amount, for six months, an equal quantity of hydrogen could not be
maintained in equal purity for six weeks.
"The supporting power being estimated at 2500 pounds, and the united
weights of the party amounting only to about 1200, there was left a
surplus of 1300, of which again 1200 was exhausted by ballast, arranged
in bags of different sizes, with their respective weights marked upon
them—by cordage, barometers, telescopes, barrels containing provision
for a fortnight, water-casks, cloaks, carpet-bags, and various other
indispensable matters, including a coffee-warmer, contrived for warming
coffee by means of slack-lime, so as to dispense altogether with fire,
if it should be judged prudent to do so. All these articles, with the
exception of the ballast, and a few trifles, were suspended from the
hoop overhead. The car is much smaller and lighter, in proportion, than
the one appended to the model. It is formed of a light wicker, and is
wonderfully strong, for so frail looking a machine. Its rim is about
four feet deep. The rudder is also very much larger, in proportion, than
that of the model; and the screw is considerably smaller. The balloon is
furnished besides with a grapnel, and a guide-rope; which latter is of
the most indispensable importance. A few words, in explanation, will
here be necessary for such of our readers as are not conversant with the
details of aerostation.
"As soon as the balloon quits the earth, it is subjected to the
influence of many circumstances tending to create a difference in its
weight; augmenting or diminishing its ascending power. For example,
there may be a deposition of dew upon the silk, to the extent, even,
of several hundred pounds; ballast has then to be thrown out, or the
machine may descend. This ballast being discarded, and a clear sunshine
evaporating the dew, and at the same time expanding the gas in the silk,
the whole will again rapidly ascend. To check this ascent, the only
recourse is, (or rather
was, until Mr. Green's invention of the
guide-rope,) the permission of the escape of gas from the valve; but, in
the loss of gas, is a proportionate general loss of ascending power; so
that, in a comparatively brief period, the best-constructed balloon must
necessarily exhaust all its resources, and come to the earth. This was
the great obstacle to voyages of length.
"The guide-rope remedies the difficulty in the simplest manner
conceivable. It is merely a very long rope which is suffered to trail
from the car, and the effect of which is to prevent the balloon from
changing its level in any material degree. If, for example, there should
be a deposition of moisture upon the silk, and the machine begins to
descend in consequence, there will be no necessity for discharging
ballast to remedy the increase of weight, for it is remedied, or
counteracted, in an exactly just proportion, by the deposit on the
ground of just so much of the end of the rope as is necessary. If,
on the other hand, any circumstances should cause undue levity, and
consequent ascent, this levity is immediately counteracted by the
additional weight of rope upraised from the earth. Thus, the balloon
can neither ascend or descend, except within very narrow limits, and its
resources, either in gas or ballast, remain comparatively unimpaired.
When passing over an expanse of water, it becomes necessary to employ
small kegs of copper or wood, filled with liquid ballast of a lighter
nature than water. These float, and serve all the purposes of a mere
rope on land. Another most important office of the guide-rope, is to
point out the
direction of the balloon. The rope
drags, either on
land or sea, while the balloon is free; the latter, consequently, is
always in advance, when any progress whatever is made: a comparison,
therefore, by means of the compass, of the relative positions of the two
objects, will always indicate the
course. In the same way, the angle
formed by the rope with the vertical axis of the machine, indicates
the
velocity. When there is
no angle—in other words, when the rope
hangs perpendicularly, the whole apparatus is stationary; but the larger
the angle, that is to say, the farther the balloon precedes the end of
the rope, the greater the velocity; and the converse.
"As the original design was to cross the British Channel, and alight as
near Paris as possible, the voyagers had taken the precaution to prepare
themselves with passports directed to all parts of the Continent,
specifying the nature of the expedition, as in the case of the Nassau
voyage, and entitling the adventurers to exemption from the usual
formalities of office: unexpected events, however, rendered these
passports superfluous.
"The inflation was commenced very quietly at daybreak, on Saturday
morning, the 6th instant, in the Court-Yard of Weal-Vor House, Mr.
Osborne's seat, about a mile from Penstruthal, in North Wales; and at 7
minutes past 11, every thing being ready for departure, the balloon was
set free, rising gently but steadily, in a direction nearly South; no
use being made, for the first half hour, of either the screw or the
rudder. We proceed now with the journal, as transcribed by Mr. Forsyth
from the joint MSS. Of Mr. Monck Mason, and Mr. Ainsworth. The body of
the journal, as given, is in the hand-writing of Mr. Mason, and a P.
S. is appended, each day, by Mr. Ainsworth, who has in preparation, and
will shortly give the public a more minute, and no doubt, a thrillingly
interesting account of the voyage.
"THE JOURNAL.
"
Saturday, April the 6th.—Every preparation likely to embarrass us,
having been made over night, we commenced the inflation this morning at
daybreak; but owing to a thick fog, which encumbered the folds of the
silk and rendered it unmanageable, we did not get through before nearly
eleven o'clock. Cut loose, then, in high spirits, and rose gently but
steadily, with a light breeze at North, which bore us in the direction
of the British Channel. Found the ascending force greater than we had
expected; and as we arose higher and so got clear of the cliffs, and
more in the sun's rays, our ascent became very rapid. I did not wish,
however, to lose gas at so early a period of the adventure, and so
concluded to ascend for the present. We soon ran out our guide-rope;
but even when we had raised it clear of the earth, we still went up very
rapidly. The balloon was unusually steady, and looked beautifully. In
about ten minutes after starting, the barometer indicated an altitude
of 15,000 feet. The weather was remarkably fine, and the view of the
subjacent country—a most romantic one when seen from any point,—was
now especially sublime. The numerous deep gorges presented the
appearance of lakes, on account of the dense vapors with which they
were filled, and the pinnacles and crags to the South East, piled in
inextricable confusion, resembling nothing so much as the giant cities
of eastern fable. We were rapidly approaching the mountains in the
South; but our elevation was more than sufficient to enable us to pass
them in safety. In a few minutes we soared over them in fine style; and
Mr. Ainsworth, with the seamen, was surprised at their apparent want of
altitude when viewed from the car, the tendency of great elevation in a
balloon being to reduce inequalities of the surface below, to nearly
a dead level. At half-past eleven still proceeding nearly South, we
obtained our first view of the Bristol Channel; and, in fifteen minutes
afterward, the line of breakers on the coast appeared immediately
beneath us, and we were fairly out at sea. We now resolved to let off
enough gas to bring our guide-rope, with the buoys affixed, into the
water. This was immediately done, and we commenced a gradual descent.
In about twenty minutes our first buoy dipped, and at the touch of the
second soon afterwards, we remained stationary as to elevation. We were
all now anxious to test the efficiency of the rudder and screw, and we
put them both into requisition forthwith, for the purpose of altering
our direction more to the eastward, and in a line for Paris. By means of
the rudder we instantly effected the necessary change of direction, and
our course was brought nearly at right angles to that of the wind; when
we set in motion the spring of the screw, and were rejoiced to find it
propel us readily as desired. Upon this we gave nine hearty cheers, and
dropped in the sea a bottle, enclosing a slip of parchment with a brief
account of the principle of the invention. Hardly, however, had we
done with our rejoicings, when an unforeseen accident occurred which
discouraged us in no little degree. The steel rod connecting the spring
with the propeller was suddenly jerked out of place, at the car end, (by
a swaying of the car through some movement of one of the two seamen we
had taken up,) and in an instant hung dangling out of reach, from the
pivot of the axis of the screw. While we were endeavoring to regain it,
our attention being completely absorbed, we became involved in a strong
current of wind from the East, which bore us, with rapidly increasing
force, towards the Atlantic. We soon found ourselves driving out to sea
at the rate of not less, certainly, than fifty or sixty miles an hour,
so that we came up with Cape Clear, at some forty miles to our North,
before we had secured the rod, and had time to think what we were about.
It was now that Mr. Ainsworth made an extraordinary, but to my fancy,
a by no means unreasonable or chimerical proposition, in which he was
instantly seconded by Mr. Holland—viz.: that we should take advantage
of the strong gale which bore us on, and in place of beating back to
Paris, make an attempt to reach the coast of North America. After slight
reflection I gave a willing assent to this bold proposition, which
(strange to say) met with objection from the two seamen only. As the
stronger party, however, we overruled their fears, and kept resolutely
upon our course. We steered due West; but as the trailing of the buoys
materially impeded our progress, and we had the balloon abundantly at
command, either for ascent or descent, we first threw out fifty pounds
of ballast, and then wound up (by means of a windlass) so much of the
rope as brought it quite clear of the sea. We perceived the effect of
this manoeuvre immediately, in a vastly increased rate of progress; and,
as the gale freshened, we flew with a velocity nearly inconceivable; the
guide-rope flying out behind the car, like a streamer from a vessel. It
is needless to say that a very short time sufficed us to lose sight of
the coast. We passed over innumerable vessels of all kinds, a few of
which were endeavoring to beat up, but the most of them lying to. We
occasioned the greatest excitement on board all—an excitement greatly
relished by ourselves, and especially by our two men, who, now under the
influence of a dram of Geneva, seemed resolved to give all scruple, or
fear, to the wind. Many of the vessels fired signal guns; and in all
we were saluted with loud cheers (which we heard with surprising
distinctness) and the waving of caps and handkerchiefs. We kept on in
this manner throughout the day, with no material incident, and, as
the shades of night closed around us, we made a rough estimate of the
distance traversed. It could not have been less than five hundred
miles, and was probably much more. The propeller was kept in constant
operation, and, no doubt, aided our progress materially. As the sun
went down, the gale freshened into an absolute hurricane, and the ocean
beneath was clearly visible on account of its phosphorescence. The wind
was from the East all night, and gave us the brightest omen of success.
We suffered no little from cold, and the dampness of the atmosphere was
most unpleasant; but the ample space in the car enabled us to lie down,
and by means of cloaks and a few blankets, we did sufficiently well.
"P.S. (by Mr. Ainsworth.) The last nine hours have been unquestionably
the most exciting of my life. I can conceive nothing more sublimating
than the strange peril and novelty of an adventure such as this. May
God grant that we succeed! I ask not success for mere safety to my
insignificant person, but for the sake of human knowledge and—for the
vastness of the triumph. And yet the feat is only so evidently feasible
that the sole wonder is why men have scrupled to attempt it before. One
single gale such as now befriends us—let such a tempest whirl forward
a balloon for four or five days (these gales often last longer) and the
voyager will be easily borne, in that period, from coast to coast. In
view of such a gale the broad Atlantic becomes a mere lake. I am more
struck, just now, with the supreme silence which reigns in the
sea beneath us, notwithstanding its agitation, than with any other
phenomenon presenting itself. The waters give up no voice to
the heavens. The immense flaming ocean writhes and is tortured
uncomplainingly. The mountainous surges suggest the idea of innumerable
dumb gigantic fiends struggling in impotent agony. In a night such as is
this to me, a man
lives—lives a whole century of ordinary life—nor
would I forego this rapturous delight for that of a whole century of
ordinary existence.
"
Sunday, the seventh. [Mr. Mason's MS.] This morning the gale, by 10,
had subsided to an eight or nine—knot breeze, (for a vessel at sea,)
and bears us, perhaps, thirty miles per hour, or more. It has veered,
however, very considerably to the north; and now, at sundown, we are
holding our course due west, principally by the screw and rudder, which
answer their purposes to admiration. I regard the project as thoroughly
successful, and the easy navigation of the air in any direction (not
exactly in the teeth of a gale) as no longer problematical. We could not
have made head against the strong wind of yesterday; but, by ascending,
we might have got out of its influence, if requisite. Against a pretty
stiff breeze, I feel convinced, we can make our way with the propeller.
At noon, to-day, ascended to an elevation of nearly 25,000 feet, by
discharging ballast. Did this to search for a more direct current, but
found none so favorable as the one we are now in. We have an abundance
of gas to take us across this small pond, even should the voyage
last three weeks. I have not the slightest fear for the result. The
difficulty has been strangely exaggerated and misapprehended. I can
choose my current, and should I find
all currents against me, I can
make very tolerable headway with the propeller. We have had no incidents
worth recording. The night promises fair.
P.S. [By Mr. Ainsworth.] I have little to record, except the fact (to me
quite a surprising one) that, at an elevation equal to that of Cotopaxi,
I experienced neither very intense cold, nor headache, nor difficulty
of breathing; neither, I find, did Mr. Mason, nor Mr. Holland, nor Sir
Everard. Mr. Osborne complained of constriction of the chest—but this
soon wore off. We have flown at a great rate during the day, and we
must be more than half way across the Atlantic. We have passed over
some twenty or thirty vessels of various kinds, and all seem to be
delightfully astonished. Crossing the ocean in a balloon is not so
difficult a feat after all.
Omne ignotum pro magnifico. Mem: at
25,000 feet elevation the sky appears nearly black, and the stars are
distinctly visible; while the sea does not seem convex (as one might
suppose) but absolutely and most unequivocally
concave.(*1)
"
Monday, the 8th. [Mr. Mason's MS.] This morning we had again some
little trouble with the rod of the propeller, which must be entirely
remodelled, for fear of serious accident—I mean the steel rod—not
the vanes. The latter could not be improved. The wind has been blowing
steadily and strongly from the north-east all day and so far fortune
seems bent upon favoring us. Just before day, we were all somewhat
alarmed at some odd noises and concussions in the balloon, accompanied
with the apparent rapid subsidence of the whole machine. These phenomena
were occasioned by the expansion of the gas, through increase of heat in
the atmosphere, and the consequent disruption of the minute particles of
ice with which the network had become encrusted during the night. Threw
down several bottles to the vessels below. Saw one of them picked up by
a large ship—seemingly one of the New York line packets. Endeavored to
make out her name, but could not be sure of it. Mr. Osborne's telescope
made it out something like "Atalanta." It is now 12, at night, and we
are still going nearly west, at a rapid pace. The sea is peculiarly
phosphorescent.
"P.S. [By Mr. Ainsworth.] It is now 2, A.M., and nearly calm, as well as
I can judge—but it is very difficult to determine this point, since
we move
with the air so completely. I have not slept since quitting
Wheal-Vor, but can stand it no longer, and must take a nap. We cannot be
far from the American coast.
"
Tuesday, the 9
th. [Mr. Ainsworth's MS.]
One, P.M. We are in
full view of the low coast of South Carolina. The great problem is
accomplished. We have crossed the Atlantic—fairly and
easily
crossed it in a balloon! God be praised! Who shall say that anything is
impossible hereafter?"
The Journal here ceases. Some particulars of the descent were
communicated, however, by Mr. Ainsworth to Mr. Forsyth. It was nearly
dead calm when the voyagers first came in view of the coast, which
was immediately recognized by both the seamen, and by Mr. Osborne.
The latter gentleman having acquaintances at Fort Moultrie, it was
immediately resolved to descend in its vicinity. The balloon was brought
over the beach (the tide being out and the sand hard, smooth, and
admirably adapted for a descent,) and the grapnel let go, which took
firm hold at once. The inhabitants of the island, and of the fort,
thronged out, of course, to see the balloon; but it was with the
greatest difficulty that any one could be made to credit the actual
voyage—
the crossing of the Atlantic. The grapnel caught at 2, P.M.,
precisely; and thus the whole voyage was completed in seventy-five
hours; or rather less, counting from shore to shore. No serious accident
occurred. No real danger was at any time apprehended. The balloon was
exhausted and secured without trouble; and when the MS. from which this
narrative is compiled was despatched from Charleston, the party were
still at Fort Moultrie. Their farther intentions were not ascertained;
but we can safely promise our readers some additional information either
on Monday or in the course of the next day, at farthest.
This is unquestionably the most stupendous, the most interesting, and
the most important undertaking, ever accomplished or even attempted by
man. What magnificent events may ensue, it would be useless now to think
of determining.
(*1)
Note.—Mr. Ainsworth has not attempted to account for this
phenomenon, which, however, is quite susceptible of explanation. A line
dropped from an elevation of 25,000 feet, perpendicularly to the surface
of the earth (or sea), would form the perpendicular of a right-angled
triangle, of which the base would extend from the right angle to the
horizon, and the hypothenuse from the horizon to the balloon. But the
25,000 feet of altitude is little or nothing, in comparison with the
extent of the prospect. In other words, the base and hypothenuse of the
supposed triangle would be so long when compared with the perpendicular,
that the two former may be regarded as nearly parallel. In this manner
the horizon of the æronaut would appear to be
on a level with the
car. But, as the point immediately beneath him seems, and is, at a great
distance below him, it seems, of course, also, at a great distance below
the horizon. Hence the impression of
concavity; and this impression
must remain, until the elevation shall bear so great a proportion to
the extent of prospect, that the apparent parallelism of the base and
hypothenuse disappears—when the earth's real convexity must become
apparent.