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precise nature of the action which produces this effect it would not be possible to assign at present; but it is worthy of note that the observations of the eclipse of 1871, by Lockyer and others, rather favor this view, by showing that hydrogen, in a feebly luminous condition, is found all around the sun, and at a very great altitude—far above the ordinary range of prominences.

The eruptive prominences are very different, consisting usually of brilliant spikes or jets, which change their form and brightness very rapidly. For the most part they attain altitudes of not more than 20,000 or 30,000 miles, but occasionally they rise far higher than even