The Observatory Volume 31

The Observatory Volume 31

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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. 1908 edition. Excerpt: ...on the red side, and, indeed, as already stated in previous correspondence, Mr. Nagaraja is perfectly aware of this, as he wrote to me under November 26, 1906, "the darkening occurs slightly to the violet side of the bright chromospheric line," in confirmation of the visual appearance of the relative position of the radiations. Perhaps the reversion of position now tabulated by Mr. Evershed is due to some clerical error, or is it possibly due to actual physical changes? In that case we might ultimately hit on an average mean of perfect coincidence of dark and bright D3. Mr. Evershed himself is ready to admit that absolute coincidence cannot be expected on account of the fact which I stated from the first, that the appearance of dark D, is due to enhanced eruptive activity at play. This is quite true, but I should hesitate to accept Mr. Evershed's explanation of the circumstance that ordinarily there is no dark line at the position D3 in the solar spectrum, and submit modestly that the explanation 1 gave in the Observatary (No. 393, p. 97, last paragraph) appeals to me as the more likely correct one. The depth of material traversed by the line of sight just outside the limb is, as he states, double of that just within the limb, but this is proportionate to the depths of the various superimposed layers, which, as the fiash--spectrum shows us, vary considerably, and is for helium no doubt subject to the same ratios as for hydrogen, &c. Indeed, there are many elements whose depth of layer is vastly less than that of helium, yet they give absorption-lines strong enough to be easily seen. Moreover, I feel sure that the depth of helium traversed by the line of sight close to, but just within the limb to be as great as the...show more

Product details

  • Paperback | 190 pages
  • 189 x 246 x 10mm | 349g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236881680
  • 9781236881687