Page:Transactions NZ Institute Volume 16.djvu/31

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The total eclipse of the sun, visible throughout this part of the world, which took place on the 6th of May last, had been looked forward to by men of science with special attention, on account of the interesting questions which it was expected to solve.

The roseate protuberances, of the chromosphere which are seen surrounding the limb of the sun during an eclipse were, by the investigations which were made during and consequent upon the eclipse of 1868, proved to be jets, composed almost exclusively of incandescent hydrogen gas, to which I before referred in speaking of the passage of the comet, bursting forth from the layers of vapour which form the atmosphere to the sun. Amongst these vapours spectrum analysis has detected sodium, magnesium, and calcium.

Beyond this atmosphere, however, there is visible during a total eclipse a magnificent silvery aureole, or luminous corona, which may reach to a distance equal to an entire' radius of the moon's orbit. It is not yet certain of what this corona is composed, and it is quite possible that it may be a magnetic phenomenon analogous to the aurora borealis. The remarkable association of the breaking-out of sun-spots with the occurrence of violent magnetic storms on the sun's surface gives support to this view. A marked instance of this occurred on the 19th November last, when telegraphic communication was interfered with throughout the world, and an aurora was visible over both hemispheres, associated with a very large sun-spot.

To the corona again immense appendices have been observed. Whether they are dependent on the coronal atmosphere, or are really streams of meteorites circulating round the sun, was still uncertain; and this was one of the questions which it was hoped would be decided by the observations taken during the eclipse of 1883, especially as bearing on the remarkable theory lately put forth by Dr. Siemens to explain the maintenance of the sun's energy, which suggests that energy thrown off from the equatorial regions of the sun is reabsorbed at the sun's poles, to be again re-formed into a source of power.

Prom the observations of the eclipse it was moreover expected that information would be furnished respecting the small round spots which have frequently been observed to appear and disappear in front of the sun's orb. Can these be planets, revolving round the sun, but which the illumination of our atmosphere, so bright in the neighbourhood of the sun, conceals from us at other times? There are but two ways in which the matter can be investigated—viz., the attentive study of the solar surface (a work of great difficulty), and the examination of the circumsolar region whilst an eclipse renders such examination possible. As ordinary eclipses have only a duration of two minutes