Spectrum Analysis; Six Lectures, Delivered in 1868, Before the Society of Apothecaries of London

Spectrum Analysis; Six Lectures, Delivered in 1868, Before the Society of Apothecaries of London : With Appendices ... Volume 7

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1870 edition. Excerpt: ...task set before us of endeavouring to explain the grounds upon which Professor Kirchhofl-concludes with certainty, that in the solar atmosphere, at a distance of about 91 millions of miles, substances such as iron, sodium, magnesium, and hydrogen, which we know well. on this earth, are present in a state of luminous gas, In beginning to consider this matter, we shall, however, do well to remember that the subject is still in its infancy; that it is only wit11in the last few years that we have been at all acquainted with the chemistry of these distant bodies. We must not be surprised to find that some of our questions cannot be satisfactorily answered, and we may expect in several instances to meet with facts to which an explanation is still wanting. In the first lecture I pointed out to you that sunlight differs from the light given off by solid and liquid substances, as well as from the light given off by gaseous bodies. If we were experimenting with sunlight now, and if I could throw the solar spectrum on to the screen, instead of this continuous spectrum of the incandescent carbon poles we should find that this bright band was out up by a series of dark lines or shadows. These lines I mentioned to you were first discovered in 1814 by F raunhofer---at least they were first carefully observed by him---and have since gone by the name of Fraunhofer's lines. Fraunhofer measured the distances (see Fig. 56) between these fixed lines, and he found that the distance from D to E, and from E to F, remained perfectly constant in the sunlight, that they are fixed lines which always appear in sunlight; and, moreover, as I think I mentioned to you on a previous occasion, he examined the light from the moon and from the planet Venus, and...show more

Product details

  • Paperback | 108 pages
  • 189 x 246 x 6mm | 209g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236745868
  • 9781236745866