THE SUN.
rounding region in this figure is blackened, although it wouldactually, as seen in the instrument, be only somewhat lessbright than the bright lines themselves.
Fig . VIII.—Showing how a series of parallel bright linesseen at different levels may indicate the form of a massof vapour rising above the general surface of the Sun.
But it was most fortunately found by Dr. Huggins (seeFig . IX.) that if the slit of the spectroscope be opened wideenough to embrace the whole image of such a mass of vapour, acoloured figure of the whole of it is formed in the neighbourhoodof each of the bright lines which the spectrum of any portionof it would produce. And these coloured images are sufficientlybright to be seen at all times in an instrument of adequatepower. It is only necessary, on any given day, to examine allround the Sun, just outside the edge of the photosphere, andthe shape or movements of any such masses of gas or vapouras we have described will be visible. Sometimes there aremany of them; at other times very few. The following is acopy of the original sketch in the Proceedings of the RoyalSociety, made by Dr. Huggins, of the first prominence, orprotuberant mass of solar vapour, seen by him with a spectro-scope having its slit widely-opened on February 13th, 1869.