CHAPTERXXXIX.CONJECTURES ON THE CAUSES OF THE CIRCULAR TRANSPARENCY TO A CERTAIN DISTANCE BELOW THE BALLOON, AND OF THE RED LIGHT FROM THE SEA AND RIVERS, WHEN SEEN ABOVE THE LEVEL OF THE SUPERIOR CLOUDS.On the circular Transparency.Section 222.QUERE: As Red is the heaviest and Blue the lightest Colour; and asredRays blended at a certain Angle withblueRays, produce Opacity: further; asredis thepredominantColour reflected from Water, while in the Form ofdenseCloud, for Instance at the Rising and Setting of the Sun; andbluethe Colour always reflected from the light Medium of Air or Sky; Does not this Mixture of least and most refrangible Rays, which, when aided with the intermediate primary ones, causes aTransparencynear and round the Eye of a Spectator placed either on Earth or among the Clouds; produce, at a greater Distance and different Angle, such a Degree of Opacity, as actually to give the Idea of Clouds surrounding him at a Distance?The latter Part at least is true, that Vapour and Air, which arenaturallyqualified totransmitredandblue, rather than any other Light, will, at a certain Angle, whenblended, produce anopacity. (See the Letter sent byNewtonfrom Cambridge to Dr. Derham, in order to be presented to the Royal Society,—in “Miscellanea Curiosa, Vol. 1, Page 109.”)On the red Light from the Sea and Rivers.Quere: May not the Rivers below act as a Prism; as Clouds, about Sun-set or Sun-rise, do to a Spectator on Earth, and reflect only the primary Colourred, theheaviestand least refrangible Ray?It being also considered that Refraction cannot change the primary Colour: nor are Rays, in the Direction from below to the Zenith, refracted; tho’ seen from a rarer into a denser Medium.Possibly, a Pencil of Rays, in coming up from the River below may be stripped or drained by the double Absorption of the Atmosphere and River, and the Colourredonly, suffered toreach the Eye: “being the last to quit its Basis the Water.” (SeeMorgan’s Observations on the Light of Bodies, &c. &c. Phil. Trans. for the Year 1785, Part 1, Vol. 75, Chap. 91.)
CHAPTERXXXIX.
On the circular Transparency.
Section 222.QUERE: As Red is the heaviest and Blue the lightest Colour; and asredRays blended at a certain Angle withblueRays, produce Opacity: further; asredis thepredominantColour reflected from Water, while in the Form ofdenseCloud, for Instance at the Rising and Setting of the Sun; andbluethe Colour always reflected from the light Medium of Air or Sky; Does not this Mixture of least and most refrangible Rays, which, when aided with the intermediate primary ones, causes aTransparencynear and round the Eye of a Spectator placed either on Earth or among the Clouds; produce, at a greater Distance and different Angle, such a Degree of Opacity, as actually to give the Idea of Clouds surrounding him at a Distance?
The latter Part at least is true, that Vapour and Air, which arenaturallyqualified totransmitredandblue, rather than any other Light, will, at a certain Angle, whenblended, produce anopacity. (See the Letter sent byNewtonfrom Cambridge to Dr. Derham, in order to be presented to the Royal Society,—in “Miscellanea Curiosa, Vol. 1, Page 109.”)
On the red Light from the Sea and Rivers.
Quere: May not the Rivers below act as a Prism; as Clouds, about Sun-set or Sun-rise, do to a Spectator on Earth, and reflect only the primary Colourred, theheaviestand least refrangible Ray?
It being also considered that Refraction cannot change the primary Colour: nor are Rays, in the Direction from below to the Zenith, refracted; tho’ seen from a rarer into a denser Medium.
Possibly, a Pencil of Rays, in coming up from the River below may be stripped or drained by the double Absorption of the Atmosphere and River, and the Colourredonly, suffered toreach the Eye: “being the last to quit its Basis the Water.” (SeeMorgan’s Observations on the Light of Bodies, &c. &c. Phil. Trans. for the Year 1785, Part 1, Vol. 75, Chap. 91.)