Page:Micrographia - or some physiological descriptions of minute bodies made by magnifying glasses with observations and inquiries thereupon.djvu/346

Rh Limb, these Rays, being by the Atmosphere inflected, appear to the eye at E, as if they had come from the points, N and O; and because the Ray L has a greater inclination upon the inequality of the atmospheree then I, therefore must it suffer a greater inflection, and consequently be further elevated above its true place, then the Ray I, which has a less inclination, will be elevated above its true place; whence it will follow, that the lower side appearing neerer the upper then really it is, and the two lateral sides, viz. the right and left side, suffering no sensible alteration from the inflection, at least what it does suffer, does rather increase the visible Diameter then diminish it, as I shall shew by and by, the Figure of the luminous body must necessarily appear somewhat Elliptical.

This will be more plain, if in the seventh Figure of the 37. Scheme we suppose A B to represent the sensible Horizon; C D E F, the body of the Sun really below it; G H I K, the same appearing above it, elevated by the inflection of the Atmosphere: For if, according to the best observation, we make the visible Diameter of the Sun to be about three or four and thirty minutes, and the Horizontal refraction according to Ticho be thereabout, or somewhat more, the lower limb of the Sun E, will be elevated to I; but because, by his account, the point C will be elevated but 29. minutes, as having not so great an inclination upon the inequality of the Air, therefore I G, which will be the apparent refracted perpendicular Diameter of the Sun, will be less then C G, which is but 29. minutes, and consequently six or seven minutes shorter then the unrefracted apparent Diameter. The parts, D and F, will be likewise elevated to H and K, whose refraction, by reason of its inclination, will be bigger then that of the point C, though less then that of E; therefore will the semidiameter I L, be shorter then L G, and consequently the under side of the appearing Sun more flat then the upper.

Now, because the Rays from the right and left sides of the Sun, &c. have been observ'd by Ricciolo and Grimaldus, to appear more distant one from another then really they are, though (by very many Observations that I have made for that purpose, with a very good Telescope, fitted with a divided Ruler) I could never perceive any great alteration, yet there being really some, it will not be amiss, to shew that this also proceeds from the refraction or inflection of the Atmosphere; and this will be manifest, if we consider the Atmosphere as a transparent Globe, or at least a transparent shell, encompassing an opacous Globe, which, being more dense then the medium encompassing it, refracts or inflects all the entring parallel Rays into a point or focus, so that wheresoever the Observator is plac'd within the Atmosphere, between the focus and the luminous body, the lateral Rays must necessarily be more converg'd towards his eye by the refraction or inflection, then they would have been without it; and therefore the Horizontal Diameter of the luminous body must necessarily be augmented.

This might be more plainly manifest to the eye by the sixth Figure; but because it would be somwhat tedious, and the thing being obvious