These flaming jets or prominences shooting out from the chromosphere are not to be seen every day by the naked eye; the dazzling light of the sun obscures them, gigantic as they are. They can be observed, however, by the spectroscope any day, and they are visible to us for a very short time during an eclipse of the sun. Some extraordinary outbursts have been witnessed. Thus the late Professor Young described one on September 7, 1871, when he had been examining a prominence by the spectroscope: It had remained unchanged since noon of the previous day--a long, low, quiet-looking cloud, not very dense, or brilliant, or in any way remarkable except for its size. At 12:30 p.m. the Professor left the spectroscope for a short time, and on returning half an hour later to his observations, he was astonished to find the gigantic Sun flame shattered to pieces. The solar atmosphere was filled with flying debris, and some of these portions reached a height of 100,000 miles above the solar surface. Moving with a velocity which, even at the distance of 93,000,000 miles, was almost perceptible to the eye, these fragments doubled their height in ten minutes. On January 30, 1885, another distinguished solar observer, the late Professor Tacchini of Rome, observed one of the greatest prominences ever seen by man. Its height was no less than 142,000 miles--eighteen times the diameter of the earth. Another mighty flame was so vast that supposing the eight large planets of the solar system ranged one on top of the other, the prominence would still tower above them.[1] [1] _The Romance of Astronomy_, by H. Macpherson. [Illustration: FIG. 5.--DIAGRAM SHOWING THE MAIN LAYERS OF THE SUN Compare with frontispiece.] [Illustration: _Photo: Royal Observatory, Greenwich._ FIG. 6.--SOLAR PROMINENCES SEEN AT TOTAL SOLAR ECLIPSE, May 29, 1919. TAKEN AT SOBRAL, BRAZIL. The small Corona is also visible.] [Illustration: FIG. 7.--THE VISIBLE SURFACE OF THE SUN A photograph taken at the Mount Wilson Observatory of the Carnegie Institution at Washington.] [Illustration: FIG. 8.--THE SUN Photographed in the light of glowing hydrogen, at the Mount Wilson Observatory of the Carnegie Institution of Washington: vortex phenomena near the spots are especially prominent.] The fourth and uppermost layer or region is that of the corona, of immense extent and fading away into the surrounding sky--this we have already referred to. The diagram (Fig. 5) shows the dispositions of these various layers of the sun. It is through these several transparent layers that we see the white light body of the sun. Sec. 2 The Surface of the Sun