| OCR Text |
Show 132 THE RAINllOW. . d f 1 things. It has Sunbeams are mdeed won er u means of findingj been remarked that we . have ;o 11 or only appear· out whether they _be thm~~t ~h:t does not in any ances of other thmg~. B . or the pleasure that way lessen either.the ms~~u-~t~o~1d subdivide all _our they give us. YJ e can 1V1 , small by the lme, "somethin(Ts" till they be 'ery d we can follow and very light in the b~lance l;o:~ them all on the the operation m~ntally tlldl wthe t wl1ether we trace verfie o f ' ' no th 1n g ·' " an · a· nature or imagm. e b~ckward the real successiOn ~ut they do not serv_e an artificial one of our ~~~~t account; so neither 1S and please us the le~s o h' h liCTht bring-s to reward light, nor the be.auttes dw 1~ ·ot' in their power of our observation, alt~r~. ~~ b~ a substance spreading pleasing, whether t t 1fn a(Ten;y which calls their over them, or _mere Yt. ;'s that we can see the properties so mto ac wn results. h divided by passing a small The sunbeam, w e~ trian ular prism of glass, parcel o_f it ~hrough 11 " a~e and therefore with which 00 "1ves m a sma er spf t? all the colours • h and per ec wn, gre_ater bng tn~ssth ·nbow and which on a v_ery whiCh are seen m. e ra1 sud when nearly settmg, dark cloud, oppos~~~ lo t.h:d very beautiful, is found is almost half a CllC efa than its bright colours. to have other proper ~~s the rainbow for that re· These cannot be f?u;~ t ~nand though th'e rain-drops cedes as we approac f 1 ' bring it apparently to our on the verdure some tmes not come up with it. very feet, all o:ur. speed can d but we cannot gain We n~ay follow 1t 1~t~h th~l~~~us;ems dark before us, upon 1t; and thong e c . . eas that we can the passage of th~ sunbetms 1-~ ~~nd K chasing the follow the bow till we os:r'~ ls (or once was) a rainbow through tht e -~~~;:hind-boys on the moors, summer amusemen Wl . b se they who took to the observation of nature, ecau had few other amusements. COLOURS OF LIGHT. 133 When the little bit of bright rainbow, or spectrum, as it is called, is examined, it is found that the beam of light is bent out of its path, and lengthened in the direction in which it is bent; and the parts nearest and most distant from the original direction of the light, which bound the length, are the ends, and the intermediate boundaries the sides. The colours lie across it from side to side ; first red, at the nearest end, then yellow, and then blue; but from the red to the yellow the colour passes through every imaginable shade of orange ; from yellow to blue, it passes through every shade of green ; and the blue fades off in brightness till it vanishes in that soft purple which often tints the clouds in the evening, and sometimes in the morning, and often gives the last tint to the clear sky. Now there is most heat in the red end ; that heat is greater without, or on the edge of the colour, than where it is most intense; and it diminishes as the blue end is approached, so as to be b3:rely, if at all, perceptible there. Heat is the grand agent in burning, the result of which is the union of the whole or part of the substance burned with that part of the atmospheric air which is called oxygen; and it also favours the union of oxygen with substances when there is merely heat but no flame. Substances which are combined with oxygen are said to be oxidized; the red end of the spectrum, which heats the most, also oxidizes the most; and that property becomes less and less till the middle is arrived at, and there it is not perceptible even by the nicest tests. That middle is in the green, just about that shade of it which we call grass-green, and seen in a well-kept lawn of fine forest grasses. At the blue or most distant end, there is a property the very opposite of that at the red ; and, like the former, it is strongest without, or at the edge of the colour, and it becomes less and less, till where the green is reached it is as imperceptible as that which begins M |
