DOI Seite / Zitierlink:
https://doi.org/10.11588/diglit.68888#0352
has sometimcs so (lowly increased, that I have observed the Bubble to be
seme hours in palling between the top and bottom.
7. Whether the appearance os the Pike of Tenerise and feveral other
high Mountains, at (o much greater a distance then seems to agree with
their respective heights, be not to be attributed to the Curvature of the
visual Ray, that is made by its palling obliquely through so difleringly
Denfe a Medium from the top to the eye very far distant in the Hori-
zon : For since we have already, I hope, made it very probable, that
there is such an inflexion of the Rays by the disfering density of the
parts of the Air j and since I have found, by several Experiments made
on places comparatively not very high, and have yet found the pressiire
iustain’d by those parts of the Air at the top and bottom, and alsb their
differing Expansions very considerable : Insomuch that I have found the
pressiire of the Atmofyhere lighter at the top of St. Paul’s Steeple in Lon-
don ( which is about two hundred foot high ) then at the bottom by a
sixtieth or fiftieth part, and the expansion at the top greater then that at
the bottom by neer about so much allo 5 for the Mercurial Cylinder at the
bottom was about 39. inches, and at the top half an inch lower 5 the Air
alsb included in the Weather-glass,that at the bottom fill d only 155. (pa-
ces, at the top fill’d 158. though the heat at the top and bottom was
found exastly the same with a scal’d Thermometer: I think it very rational
to suppose , that the greatest Curvature of the Rays is made nearest the
Earth,and that the inssexion of the Rays, above 3. or 4. miles upwards, is
very inconsiderable, and therefore that by this means such calculations of
the height of Mountains, as are made from the distance they are visible in
the Horizon,from the supposal that that Ray is a straight Line (that from
the top of the Mountain is, as’twere, a Tangent to the Horizon whence it
isseen) which really is a Curve., is very erroneous. Whence, I suppofe,pro-
ceeds the reason of the exceedingly disfering Opinions and Assertionsof
feveral Authors, about the height of several very high Hills.
8. Whether this Inssection of the Air will not very much alter the sup-
pofed distancesof the Planets, which seemto have a very great depen-
dence upon the Hypothetical refraction or inssexion of the Air, and that
refraCtion upon the hypothetical height and density os the Air: For
since ( as I hope ) I have here shewn the Air to be quite otherwife then
has been hitherto suppos’d, by manifesting it to be, both of a vast , at
lealt an uncertain, height, and of an unconstant and irregular density 5
It must necessarily follow, that its inssection must be varied accordingly:
And therefore we may hence learn, upon what sure grounds all the A-
stronomers hitherto have built, who have calculated the distance of the
Planets from their Horizontal Parallax 5 for since the RefraCtion and Pa-
rallax are so nearly ally’d, that the one cannot be known without the
other, especially by any wayes that have been yet attempted, how uncer-
tain must the Parallax be,when the RefraCtion is unknown? And how easie
is it for Astronomers to asiign what distance they pleafe to the Planets,and
defend them,when they have such a curious fobtersuge as that of RefraHi-
on,wherein a very little variation will allow them liberty enough to place
the Celestial Bodies at what distance they please. Is
seme hours in palling between the top and bottom.
7. Whether the appearance os the Pike of Tenerise and feveral other
high Mountains, at (o much greater a distance then seems to agree with
their respective heights, be not to be attributed to the Curvature of the
visual Ray, that is made by its palling obliquely through so difleringly
Denfe a Medium from the top to the eye very far distant in the Hori-
zon : For since we have already, I hope, made it very probable, that
there is such an inflexion of the Rays by the disfering density of the
parts of the Air j and since I have found, by several Experiments made
on places comparatively not very high, and have yet found the pressiire
iustain’d by those parts of the Air at the top and bottom, and alsb their
differing Expansions very considerable : Insomuch that I have found the
pressiire of the Atmofyhere lighter at the top of St. Paul’s Steeple in Lon-
don ( which is about two hundred foot high ) then at the bottom by a
sixtieth or fiftieth part, and the expansion at the top greater then that at
the bottom by neer about so much allo 5 for the Mercurial Cylinder at the
bottom was about 39. inches, and at the top half an inch lower 5 the Air
alsb included in the Weather-glass,that at the bottom fill d only 155. (pa-
ces, at the top fill’d 158. though the heat at the top and bottom was
found exastly the same with a scal’d Thermometer: I think it very rational
to suppose , that the greatest Curvature of the Rays is made nearest the
Earth,and that the inssexion of the Rays, above 3. or 4. miles upwards, is
very inconsiderable, and therefore that by this means such calculations of
the height of Mountains, as are made from the distance they are visible in
the Horizon,from the supposal that that Ray is a straight Line (that from
the top of the Mountain is, as’twere, a Tangent to the Horizon whence it
isseen) which really is a Curve., is very erroneous. Whence, I suppofe,pro-
ceeds the reason of the exceedingly disfering Opinions and Assertionsof
feveral Authors, about the height of several very high Hills.
8. Whether this Inssection of the Air will not very much alter the sup-
pofed distancesof the Planets, which seemto have a very great depen-
dence upon the Hypothetical refraction or inssexion of the Air, and that
refraCtion upon the hypothetical height and density os the Air: For
since ( as I hope ) I have here shewn the Air to be quite otherwife then
has been hitherto suppos’d, by manifesting it to be, both of a vast , at
lealt an uncertain, height, and of an unconstant and irregular density 5
It must necessarily follow, that its inssection must be varied accordingly:
And therefore we may hence learn, upon what sure grounds all the A-
stronomers hitherto have built, who have calculated the distance of the
Planets from their Horizontal Parallax 5 for since the RefraCtion and Pa-
rallax are so nearly ally’d, that the one cannot be known without the
other, especially by any wayes that have been yet attempted, how uncer-
tain must the Parallax be,when the RefraCtion is unknown? And how easie
is it for Astronomers to asiign what distance they pleafe to the Planets,and
defend them,when they have such a curious fobtersuge as that of RefraHi-
on,wherein a very little variation will allow them liberty enough to place
the Celestial Bodies at what distance they please. Is