Notes

Abstract

M. JANSSEN has addressed to the French Academy of Sciences the following letter, on the principal consequences to be drawn from his observations on the solar eclipse of 12th December last; it is dated Sholoor, December 19, 1871:—“I had the honour,” he says, “of sending you on the very day of the eclipse a few lines to inform the Academy that I had observed the eclipse under an exceptional sky, and that my observations led me to assume a solar origin for the Corona (see NATURE, vol. v. p. 190). Immediately after the eclipse I was obliged to busy myself with the personal and material arrangements for my expedition into the mountains, and hence I have been unable to complete any detailed account, but I take advantage of the departure of this courier to give some indispensable details as to the announced results. Without entering into a discussion, which will form part of my narrative, I shall say, in the first place, that the magnificent Corona observed at Sholoor showed itself under such an aspect that it seemed to me impossible to accept for it any cause of the nature of the phenomena of diffraction or reflection upon the globe of the moon, or of simple illumination of the terrestrial atmosphere. But the arguments which militate in favour of an objective and circumsolar cause, acquire invincible force when we inquire into the luminous elements of the phenomenon. In fact, the spectrum of the Corona appeared in my telescope, not continuous, as it had previously been found, but remarkably complex. I detected in it, though much weaker, the brilliant lines of hydrogen gas, which forms the principal element of the protuberances and chromosphere; the brilliant line which has already been indicated during the eclipses of 1869 and 1870, and some other fainter ones; obscure lines of the ordinary solar spectrum, especially that of sodium (D); these lines are much more difficult to perceive. These facts prove the existence of matter in the vicinity of the sun; matter which manifests itself in total eclipses by phenomena of emission, absorption, and polarisation. But the discussion of the facts leads us still further. Besides the cosmical matter independent of the sun which must exist in its neighbourhood, the observations demonstrate the existence of an excessively rare atmosphere, with a base of hydrogen, extending far beyond the chromosphere and protuberances, and deriving its supplies from the very matter of the latter—matter which is projected with so much violence, as we may ascertain every day. The rarity of this atmosphere at a certain distance from the chromosphere must be excessive; its existence, therefore, is not in disagreement with the observations of some passages of comets close to the sun.”