COINCIDENCE OF THE LINES OF IRON WITH THOSE OF THE SOLAR SPECTRUM Fig 91⁄2 spectrum differs in certain respects from that beautiful spectrum of the electric arc light with which much is now being done in photo-therapeutics, etc. It differs in this way, that the solar spectrum consists, not of a continuous band passing without a break or interruption from the red to the violet, through all the shades of color which we know as with what is constantly passing around us in nature. As early as 1815 Frauenhofer, a Bavarian optician, studied with care the violet spectrum and sought to discover some fixed points in it which might be independent of the nature of the prisms, and which could be regarded as points of reference to which the zones and colors of the spectrum might be referred; when he perceived that, by giving the prism a certain special position, there suddenly appeared in the spectral & b 2 $6 оворир прв авито грозд Fig. 10. The original Frauenhofer's spectrum. Fraunhofer's Abh. Denkschr. 1814_15. are placed as follows: The first at the limit of the red, the second in the middle of that color, the third near the orange the fourth at the end of that tint, the fifth in the green, the sixth in the blue, the seventh in the indigo, the eighth at the end of the violet. These are, then, the principal black lines which we distinguish in the spectrum. As to the total number of these lines, it is really amazing. Frauenhofer counted 600 with a microscope; later Brewster carried this number to 2,000; now we count 5,000 and more. (See Figure 92.) These lines of the solar spectrum are constant and invariable at all times when the sepctrum studied is that of light emanating from the sun; whatever this light may be, we find them in daylight, in that form in the clouds, in the light reflected by mountains, buildings, and all terrestrial objects. We find them even in the light of the moon and in that of the planets, because these celestial bodies shine only by the light which they receive from the sun and reflect into space. This discovery of microscopical lines which thus cross the solar spectrum was soon made fruitful by another not less important discovery. Admitting thro' a prism rays issuing from a luminous terrestrial source, such as an electric arc light, a gas jet, a lamp, a metal in fusion, etc., we notice at first that these artificial lights give rise to a spectrum as well as that of the sun, but that this spectrum differs from the solar spectrum by the number and arrangement of the colors: we remark in the second place—and here is the import image dark lines crossing the stream ant point-that the spectrum of these lights is also crossed by lines, that the distribution of these lines differs according to the nature of the light observed, and in short, that they present an invariable order, characteristic of each of them. In order to fix our ideas, let me describe an experiment such as was made as not to give a spectrum itself.] The moment we place in the flame the prepared platinum wire a spectrum appears in the telescope and the eye placed at the microscope can analyze it at its ease. This spectrum is that of the substance which burns. The luminous ray leaving the point L (Fig. 11) is reflected from the little prism O at the end of SPECTROSCOPE Fig. 11 by Kirchhoff and Bunsen, the two physicists to whom we owe these brilliant researches. Let us place in a gas jet a platinum wire, at the extremity of which we put a small fragment of the substance which we wish to analyze. Before the flame is placed the spectroscope, a telescope expressly constructed for our analysis, and in which the rays from the flame pass through a prism and an analysis microscope. [The flame of our light from whatever source, is regulated and weakened so the telescope, and thus appears to come from L. Following the axis of the telescope it is refracted successively through six prisms, A, B, G, D, E, H, and enters the telescope, K, by which it is observed. In order to compare or measure it, we should have in the little telescope, F, an image or a scale which serves to fix the position of the rays. For example, we dip the platinum wire into a bottle of potash. The moment we place it in the gas jet, a spectrum appears in the spectroscope; this is salt burns we kindle a brilliant Drummond light, and if we superpose the two spectra, immediately the yellow line of sodium will disappear from the spectrum of sodium and give place to a dark line occupying precisely the same place. It follows from this double observation that the black lines of the solar spectrum prove: I. The existence of a burning and gaseous atmosphere around that body. 2. The presence in that atmosphere of substances announced by the lines in question. There have been identified, line for line, in the sun, the 460 lines of the spectrum of iron', the 118 of titanium, 175 of calcium, 57 of magnesium, 33 of nickel, etc. So that we now know certainly that there are at the surface of that dazzling star, and in the gaseous state, iron, titanium, calcium, maganese, nickel, cobalt, chromium, sodium, barium, magnesium, copper, potassium; but we still cannot recognize any trace A USEFUL LIFE? A Denver gentleman, aged sixty-four years, we are informed, has walked over 14,000 miles since August, 1891, thus warding off pulmonary consumption, with which he was threatened, and gaining forty-two pounds in weight. This pedestrian has received money, food, and clothing contributed by casual charitable or amazed acquaintances. Far be it from us to say that our hero's performance is not a superb object-lesson as to the value of open-air life in tuberculous disease, but it does seem as of gold, silver, antimony, arsenic or mercury. Hydrogen was discovered in 1868; oxygen must exist in this furnace, but the oxygen lines which have been found in the solar spectrum proceed from our own atmosphere (Jansen 1888). Amongst all the discoveries of modern investigation none has deservedly attracted more attention or called forth more general admiration than the result of the application of spectrum analysis to chemistry. Nor is this to be wondered at when we remember that such a power has thus been placed in the hands of the chemist and allied scientists, enabling them to detect the presence of chemical substances with a degree of delicacy and accuracy hitherto unheard of, and thus to obtain a far more intimate knowledge of the composition of terrestrial matter than they formerly enjoyed. Since its discovery, the sciences in their various branches of analysis have profited much by it, in new discoveries. To be continued. if he might have varied with advantage his somewhat monotonous methods by occasionally sawing wood, mowing or reaping, doing chores around a shorthanded barn, or otherwise giving more or less for value received in other ways than by merely reciting his possibly estimable autobiography to country householders. His system lends itself regrettably to the interpretation of being hardly more than an ingenious variant of the yarn of the ordinary tramp (hobo communis).-N. Y. MedJour, and Phil. Med. Jour. 'Prof. Roland has found over 2,000 lines of iron in the solar spectrum. J. E. G. |