Rensselaer Union, Volume 7, Number 45, Rensselaer, Jasper County, 29 July 1875 — What We Learn from the Spectroscope. [ARTICLE]

What We Learn from the Spectroscope.

Home and School concludes an interesting article on the use of this valuable invention thus: There is, however, another source of evidence, in some respects more reliable and more satisfactory than change of position, which the last quarter of a century has put into the hands of men of science, and that is the spectroscope. In all these cases where the motion is in the line with our own, and in which consequently no change of apparent place is to be expected, the spectroscope renders most important service, especially if foe rate of approach or departure be very rapid. For example, Sirius, the brightest of the fixed stars, seems to be moving rapidly; but at what rate the telescope wnth the nicest micrometers would vainly seek to tell. A skillful use of the spectroscope, however, has revealed the fact that it is moving at the enormous rate of thirty miles a second, or 100,000 miles the hour. So reliable are the decisions of this wonderful instrument that a celebrated English lecturer on astronomy, a few years since, staked his reputation on the fact that certain stars which he named in and about the constellation of the Great Bear are moving with great rapidity either to or from foe earth, he could not tell which, only that they are moving in the same direction, and that certain others in the same neighborhood are moving in another direction. The decision of these points was left to foe spectroscope, and when at last foe instrument was applied by the expert spectroscopists of the day the result was exactly as had been predicted; and five of the stars were proved to be receding from foe earth at the rate of about thirty miles per second ; and yet foe light which told fois tale through the spectroscope must have left those stars twenty-five or thirty, perhaps 100, years ago.