the works of edgar allan poe-1-第12章
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miles in question； and I could not help thinking that the subject
admitted room for doubt and great latitude for speculation。
〃But； in point of fact； an ascension being made to any given
altitude； the ponderable quantity of air surmounted in any farther
ascension is by no means in proportion to the additional height
ascended （as may be plainly seen from what has been stated before）；
but in a ratio constantly decreasing。 It is therefore evident that；
ascend as high as we may； we cannot； literally speaking； arrive at a
limit beyond which no atmosphere is to be found。 It must exist； I
argued； although it may exist in a state of infinite rarefaction。
〃On the other hand； I was aware that arguments have not been wanting
to prove the existence of a real and definite limit to the
atmosphere； beyond which there is absolutely no air whatsoever。 But a
circumstance which has been left out of view by those who contend for
such a limit seemed to me； although no positive refutation of their
creed； still a point worthy very serious investigation。 On comparing
the intervals between the successive arrivals of Encke's comet at its
perihelion； after giving credit； in the most exact manner； for all
the disturbances due to the attractions of the planets； it appears
that the periods are gradually diminishing； that is to say； the major
axis of the comet's ellipse is growing shorter； in a slow but
perfectly regular decrease。 Now； this is precisely what ought to be
the case； if we suppose a resistance experienced from the comet from
an extremely rare ethereal medium pervading the regions of its orbit。
For it is evident that such a medium must； in retarding the comet's
velocity； increase its centripetal； by weakening its centrifugal
force。 In other words； the sun's attraction would be constantly
attaining greater power； and the comet would be drawn nearer at every
revolution。 Indeed； there is no other way of accounting for the
variation in question。 But again。 The real diameter of the same
comet's nebulosity is observed to contract rapidly as it approaches
the sun； and dilate with equal rapidity in its departure towards its
aphelion。 Was I not justifiable in supposing with M。 Valz； that this
apparent condensation of volume has its origin in the compression of
the same ethereal medium I have spoken of before； and which is only
denser in proportion to its solar vicinity？ The lenticular…shaped
phenomenon； also called the zodiacal light； was a matter worthy of
attention。 This radiance； so apparent in the tropics； and which
cannot be mistaken for any meteoric lustre； extends from the horizon
obliquely upward； and follows generally the direction of the sun's
equator。 It appeared to me evidently in the nature of a rare
atmosphere extending from the sun outward； beyond the orbit of Venus
at least； and I believed indefinitely farther。｛*2｝ Indeed； this
medium I could not suppose confined to the path of the comet's
ellipse； or to the immediate neighborhood of the sun。 It was easy； on
the contrary； to imagine it pervading the entire regions of our
planetary system； condensed into what we call atmosphere at the
planets themselves； and perhaps at some of them modified by
considerations； so to speak； purely geological。
Having adopted this view of the subject； I had little further
hesitation。 Granting that on my passage I should meet with atmosphere
essentially the same as at the surface of the earth； I conceived
that； by means of the very ingenious apparatus of M。 Grimm； I should
readily be enabled to condense it in sufficient quantity for the
purposes of respiration。 This would remove the chief obstacle in a
journey to the moon。 I had indeed spent some money and great labor in
adapting the apparatus to the object intended； and confidently looked
forward to its successful application； if I could manage to complete
the voyage within any reasonable period。 This brings me back to the
rate at which it might be possible to travel。
〃It is true that balloons； in the first stage of their ascensions
from the earth； are known to rise with a velocity comparatively
moderate。 Now； the power of elevation lies altogether in the superior
lightness of the gas in the balloon compared with the atmospheric
air； and； at first sight； it does not appear probable that； as the
balloon acquires altitude； and consequently arrives successively in
atmospheric strata of densities rapidly diminishing I say； it does
not appear at all reasonable that； in this its progress upwards； the
original velocity should be accelerated。 On the other hand； I was not
aware that； in any recorded ascension； a diminution was apparent in
the absolute rate of ascent； although such should have been the case；
if on account of nothing else； on account of the escape of gas
through balloons ill…constructed； and varnished with no better
material than the ordinary varnish。 It seemed； therefore； that the
effect of such escape was only sufficient to counterbalance the
effect of some accelerating power。 I now considered that； provided in
my passage I found the medium I had imagined； and provided that it
should prove to be actually and essentially what we denominate
atmospheric air； it could make comparatively little difference at
what extreme state of rarefaction I should discover it that is to
say； in regard to my power of ascending for the gas in the balloon
would not only be itself subject to rarefaction partially similar （in
proportion to the occurrence of which； I could suffer an escape of so
much as would be requisite to prevent explosion）； but； being what it
was； would； at all events； continue specifically lighter than any
compound whatever of mere nitrogen and oxygen。 In the meantime； the
force of gravitation would be constantly diminishing； in proportion
to the squares of the distances； and thus； with a velocity
prodigiously accelerating； I should at length arrive in those distant
regions where the force of the earth's attraction would be superseded
by that of the moon。 In accordance with these ideas； I did not think
it worth while to encumber myself with more provisions than would be
sufficient for a period of forty days。
〃There was still； however； another difficulty； which occasioned me
some little disquietude。 It has been observed； that； in balloon
ascensions to any considerable height； besides the pain attending
respiration； great uneasiness is experienced about the head and body；
often accompanied with bleeding at the nose； and other symptoms of an
alarming kind； and growing more and more inconvenient in proportion
to the altitude attained。｛*3｝ This was a reflection of a nature
somewhat startling。 Was it not probable that these symptoms would
increase indefinitely； or at least until terminated by death itself？
I finally thought not。 Their origin was to be looked for in the
progressive removal of the customary atmospheric pressure upon the
surface of the body； and consequent distention of the superficial
blood…vessels not in any positive disorganization of the animal
system； as in the case of difficulty in breathing； where the
atmospheric density is chemically insufficient for the due renovation
of blood in a ventricle of the heart。 Unless for default of this
renovation； I could see no reason； therefore； why life could not be
sustained even in a vacuum； for the expansion and compression of
chest； commonly called breathing； is action purely muscular； and the
cause； not the effect； of respiration。 In a word； I conceived that；
as the body should become habituated to the want of atmospheric
pressure； the sensations of pain would gradually diminish and to
endure them while they continued； I relied with confidence upon the
iron hardihood of my constitution。
〃Thus； may it please your Excellencies； I have detailed some； though
by no means all； the considerations which led me to form the project
of a lunar voyage。 I shall now proceed to lay before you the result
of an attempt so apparently audacious in conception； and； at all
events； so utterly unparalleled in the annals of mankind。
