the works of edgar allan poe-1-第60章
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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 battledoor； 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 鎟onaut 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 鎟ial
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 鎟ostation。 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
