SPECTRUM ANALYSIS.

Kaipara and Waitemata Echo, 8 May 1914, Page 2

SPECTRUM ANALYSIS.

(By EPfiAR LUCiE.V LARKIKT.)

Spectrum chemistry is now one of the most coiiihietft, elaborate, and exalted sciences, ri.nU.ing with mathematics and astronomy. Darken a room with heavy internal shutters, one having south windows, in any north latitude. On the north w.wl place a white screen, a sheet of white cloth, or, better, a plaster of paris wall. Make a narrow, vertical slit, two inches long, in the window shutter. Let this slit have lur.abk1 o-iy t., so it can be made of variable width from 1-32 to 1-200 of an inch. Sot a mirror outside, so as to reflect rays direct from the sun through this narrow slit of light on the north white wall. Now f)ln.ee a triangular glass nrism in the beam of light, and behold on the white surface one of the most beautiful visions in all nature —the spectrum of the sun, a long band of , original primal colours. A very remarkable effect is wrought by the prism. The strip of whitu sunlight is separated into a long belt of colours, but the entire ba::.l is shifted sidewise, not a ray fulls on the s;tot where the fir.'-.l narr.r.v strip fell. Not only this, but -the primary colours have different places at different distances from the first point. The order is red, orange, yellow, given, blue, indigo, violet. The red is bent out of its straight course the least and violet the farthest. The width of the band i:s equal to the height of the slit. Now p'.;t a lens in a position to magnify, and the band of gorg-:ur; colours will be much lonccr. Cut off sunlL ht and put an electric arc in front of the slit —the spectrum will be the same on the screen nrs from the sun, apparently, that is, continuous from red to violet, all colours present to ordinary view. So Newton, who made those original researches, wrote this law : "White light is composed of all th."> original colours ;" and he died without knowing that white sunlight is not really continuous. Two centuries later, by moans of improved slits, additional len.e.s and apparatus it was discovered that fine black lines crossed the band at right angles. Those cannot be seen by the unaided eye, and the very fine require powerful microscopic lenses to be made vifible. After 275 years of very arduous work, modern scientific men are in possession of a perfect spectroscope, whose sole office is to analyse any 1 i-ht that may be projected into its fine and delicate slit. But what shall be said of the fine black lines ? How summon words to tell of their vast importance ? What in all science exceeds in value these black Fruiinhofer lines ? Spneewaves alone equal them in value. For these mysterious lines, after two hundred years of careful research, were finally discovered to be nothing lesr; than the Mrhiiiel of Nature. Like the Morse signals, they convey fr<>m Nature to man siy;ns and symbols revealing vhe most hidden secrets. Every one of the eighty-five elements known to chen.iots projects different sets of lines (.n :.he. screen. No tv ro are alike. Nome project two or three and others tens, fifties, hundreds. Some hutnlredths and others thousands of an inch in thickness. How these lines are interpreted and read cannot even be alluded to in a note like this. One cardinal fact, however, must be mentioned, thus : JWake a long rule or scale on the wall showing inches and sixteenths ; then with the same prism and lenses, the black lines always fall on the same ruling on the scale. Thus, no two elements will present lines falling in exactly the same place. "Will present" requires explanation. How can iron, copper, tin, platinum, or gold "present" light ? These metals must all be red-need to gas in the fierce heat of the electric arc in front of the slit. Then their sets of bright lines will be" presented, or projected, by the prism and lenses, each in its changeless place. Hand am thing to a spectroscopist, ask him to analyse it. He | will turn it to white hot gas, pass i the light into the slit, put his eye ' to the observing telescope, read the magnified scale, and make his reply. One part in one trillion of any element in any complex compound ! can Lie detected. I All chemistry was thus revolution- , ised and set upon a high and enduring base as of rigid mathe- i mati'-s. Turn the slit toward the sun and full upon the stars, sepa- ' rate the light, read the linos, and ] tell what elements are glowing in all directions in suns in spacedeeps.—"London 'Budget."