Atwood Hammond High School - Post Yearbook (Atwood, IL)

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particles of carbon floating in them, gases and vapors under great pressure, and, in general, all white hot solids or liquids, are sent through the prism of the spectroscope, separately, of course, their spectra are found to be continuous. Those of rarefied vapors and gases, heated to incandescence, or burning, are discontinuous. And every burning vapors and gas give off its own particular color and reinforces the same one on the spectrum, making it appear much plainer than the others. Thus, for example, if we burn sodium carbonate with platinum, the latter of which ordinarily gives off a continuous spectrum, we tind two splendid yellow lines, so near together that they are often taken for one. Lithium gives a red line; hydrogen gives three: red, greenish blue, and dark blue. Rut now, if instead of burning the gases and vapors with a white light, such as that from white hot platinum, we merely allow the rays from the platinum to pass through the vapor into the collimator, we observe a dark-line spectrum. Suppose that in place of burning the sodium carbonate with the platinum we allowed the ravs from the latter to pass through sodium vapor, when not burning. There wou'd appear two dark lines in the exact spots where we saw the bright yellow ones before. If we used lithium a dark line would take the place of the red one. From experiments with various and numerous substances we have the Principle of Reversal, namely, that a burning gas or vapor gives off and reinforces that same color on the spectrum of white light which it absorbs when the rays of white light passthrough it while it is not burning. The spectrum of sunlight, the solor spectrum, is an absorption or dark-lined one. This fact was first noticed by Wollaston in 1802. Fraunhofer claimed that there were no less than live hundred seventy six ol these dark lines. Later physicists have tound their number to be unlimited. Stokes in 185 2 tirst made a suggestion as to their cause and his theory which has been accepted was fully established by Kirchhoff in 1859. His idea was that the white-hot surface ot the sun. called the photosphere, would by itself produce a continuous spectrum. An atmosphere of glowing vapors, called the chromosphere, exists outside the photosphere. Its temperature is less than that of the photosphere but nevertheless great enough to keep metals in the vapor state. As the light passes ihrough the elm m •-sphere the cooler vapors there absorb contain certain rays. This accounts for the so called Fraunhofer lines. By this means we are able to tell the presence of sodium, hydrogen, iron, magnesium, calcium and many other elements in the sun. And this examination is not limited to the sun alone but has been made on other heavenly bodies. Their chemistry is also .known by spectroscopy. Spectra of comets have been studied. They were usually continuous except for three bright bands, one in'the yellow, one in tbe

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now, not only its cause is known, but through it many facts have been ascertained concerning the nature of the sun and other heavenly bodies. According to Newton's explanation, the one that is unquestionably accepted, tie white or colorless light frtm the sun is a mixture of an infinite number of differently colored rays. A ray of light, in passing from a rarer to a denser medium, as from air to glass, is bent or refracted from a straight course. But all rays are not equally refrangible, that is they are notall bent the same amount the red being the least and the violet the most. This difference in the rays produces the colored ribbon, called the solar spectrum, when the sun's rays are allowed to pass through a prism. Newton divided the spectrum into seven different spaces which he called red, orange, yellow, green, blue, indigo, and violet, named in the order of their refrangibility and their consequent positions in the spectrum. A method was mentioned if not put into operation by Newton which has since been employed in proving that the sunlight contains rays of every refrangibility from the highest to the lowest. Therefore, there is no scientific foundation for his distinct separation of the spectrum. Experiments show three kinds of spectra. The first, continuous, is one of a gradual change from one shade to another with no sharp partitions between them. The second is called discontinuous or bright-lined, and certain shades in it are much more brilliant than others. The last one is the reverse of the second and has dark lines iustead of bright ones. Spectra of the last sort are termed absorption or dark -lined spectra. These three kinds of spectra form the basis on which the study of spectroscopy is built. The instrument used in examining spectra is called the spectroscope. It might be well to describe its mechanism. Light enters a small opening in the end of a cylinder called a collimator. This contains a convex lens which makes the ravs fall parallel on a glass prism at the other end of the collimator. The light passes through the prism and alter emerging on the adjacent side it enters a telescope. A third tube contains a lens and a graduated scale which is illuminated by a lamp, stationed at the end of the tube, and so placed that parallel rays from the scale are reflected from the face of the prism into the telescope. Thus the image of the scale and that of the spectrum are visible at the same time. By slowly rotating the prism an extremely small part of the spectrum is magnified and seen through the telescope. Thus if a very minute portion of the spectrum were brighter than the rest, it would be plainly visible. The scale shows the exact position of such a point on the spectrum, the slightest movement of the prism being indicated. It an electric light, lime light, lights from white-hot platinum, lamps and candles, the last two, because of the

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green, and another in the blue. A fortli band is sometimes visible in the violet. The green band, which is the most brilliant of the three, in sotne cases is crossed by a number ot fine, bright lines and there are traces of s'milar lines in the yellow and blue bands. This spectrum is exactly the same as that given bv the blue base of an ordinary gas or candle flame. This indicates the presence of sonr gaseous carbon compound in the comet. Although it is very difficult to catch the spectrum of a shooting star, it has been done occasionally It shows that sodium and probably magnesium exist in meteors. One of the earliest achievements of the spectroscope was its demonstration of the pretence ot hydrogen and helium in the nebulae. The spectra of Character Sketches ROSALIND, By Lora Bijfgs To me Rosalind is the most interesting character in Shake-sphere’s, “As You Like It. “She represents an ideal of true womanhood. In reading this comedy Rosalind is a figure that is easily fixed upon one’s mind and afterwards in thinking of the play he at once recalls a picture of her. I imagine her to be a young lady who possessed a certain dignity, which everyone recognized, and which was even noticeable though she disguised herself by wearing man’s apparel. A look at Rosalind’s face would convince a person of her good dis-posi.ion. The other characters the stars vary, but Secchi and Vogel classified them under four and three divisions, respectively. They both agreed that some were almost identical with the solar spectrum. The spectroscope may also be put to a more practical use as tracing adulterations in food or poison in the blood. The power to detect extremely small amounts of such things it a valuable one: Professor Swan stated that lie discovered one-two million, five hundred thousandth part of a grain of sodium with the spectroscope. Stokes traced, by the change of absorption bands produced by the coloring matter ot blood,the oxidation and reduction which constantly takes place in this substance, and its connection with the distinction between venous and arterial blood. From “As You Like It.” in the play liked Rosalind, for she had a power toconfer happiness, hence she made friends with everyone. She had sor row's and troubles, but they were hidden behind a mask of cheerful 1 ness. Rosalind was not so clever in making plans as her cousin, Celia, but by her gay humor and ready wit she cairied outmost daring plans. This is shown bv the way in which she so successfully acted tl e man after Celia proposed the plan of disguising themselves and traveling to the forest of Arden Ft;,l she commands our respect; for her male attire, mannish talk, and actions bring outeven more