37 8

Of Light and Colours.

ther at G or H, to form a strong and dis*tinct Image of the Sun; which Rays,

therefore,

31. Now let S P be a Line drawn through the Spec-tator’s Eye at A, parallel to the Sun’s Rays S N, andconceive the several Rays G R turning about the Line

) A P as an Axis, and always under the fame invariableAngle GRP; ’tis evident, the Extremity of each Raywould in the Cloud or Rain describe a Circle whichwould be the Base of a Cone whose Axis is A P, andits Vertex A ; and for the same Reason that the Drop Aexcites the Sensation of Red, every Drop in the Circledescribed by the Extremity of the Ray G R will excitethe same Sensation ; thus will a red circular Arch AHbe formed as far as the Rain extends. Next to that theRay B A, by revol ving, describes the Arch of an OrangeColour, as BI; the Ray CA will in like manner traceout the Yellow Circumference, as CK-, and so of allthe rest, as represented in the Figure .'

32. Hence the Second Phanomenon, viz. the circulars-Form, is accounted for; and also the Third, which isthe Breadth of the Bow ; for that will be equal to the

PI XLI Angle /RG = RGV = i° 45', where the Ray, asEia; 2 ' here, Emerges after one Reflection. These Particulars’ are represented more compleatly in the Figure, whereB G D is the red Circumference formed by the Rctaticriof the Ray A G, that can first come to the Eye at A}and C g E is the V iolet Arch formed by the least re-frangible Ray g A; after which the Rays are all re-fracted below the Eye. And thus by the interme-diate Rays and Colours the whole interior Boyy is pro-duced. ‘

33. The Fourth Phanomenon is the Appearance of TvJOBows. This follows from hence, that after an efficaciousRay of Light S N, entering a Drop of Rain, has beentwice reflected on the farthest Side at F and H, it wiUemerge refracted into all its simple or constituent Rays atG upon the upper Side of the Drop, so as to make withthe incident Ray the Angle GYN or 8 YA — 54° 1° »,if that Ray be the Violet Sort, or most refrangible, (byArt. 26.) but if it be of the red or least refrangible

' Sort,,