The last of the solar appendages, the corona, can only be seen during total eclipses. The researches of Young and Janssen indicate that it is partly gaseous and partly meteoric in its constitution; and various photographs, taken at the eclipses since 1870, have demonstrated its variation in shape, which is in harmony with the eleven-year period. Several attempts have been made to observe the corona without an eclipse. In 1882 Huggins made the attempt, but failed, and Hale, with his photographic process, had no better success. More recently, in 1904, a Russian astronomer, _Alexis Hansky_, observing from the top of Mont Blanc, secured some photographs on which he believes the corona is represented, but so far his observations have not been confirmed by other astronomers. The application of the spectroscope to the motions on the solar surface is perhaps one of the most wonderful triumphs in astronomical science. In 1842 _Christian Doppler_ (1803-1853), Professor of Mathematics at Prague, had expressed the view that the colour of a luminous body must be changed by its motion of approach or recession. It was obvious to Doppler that if the body was approaching, a larger number of light waves must be entering the eye of the observer than if it were retreating. Miss Clerke thus illustrates Doppler’s principle: “Suppose shots to be fired at a target at fixed intervals of time. If the marksman advances, say, twenty paces between each discharge of his rifle, it is evident that the shots will fall faster on the target than if he stood still; if, on the contrary, he retires by the same amount, they will strike at correspondingly longer intervals.” It occurred to various astronomers that it would be possible to measure cyclones and hurricanes in the Sun, not by change of colour in the spectrum, but by the shifting of the lines; and in 1870 this was successfully done by Lockyer. In the next few years efforts to measure the solar rotation were made by Young, Zöllner, and others, who succeeded in measuring the displacement of the lines, but not the time of rotation. This was reserved for the famous Swedish astronomer, Dunér. _Nils Christopher Dunér_, born in 1839 in Scania, was employed as an assistant at Lund Observatory from 1858 to 1888, when he was appointed director of the Observatory at Upsala. In that year he commenced a study of the solar rotation, measuring it by means of Doppler’s principle. He confirmed the telescopic work of Carrington and Spörer on the equatorial acceleration, and measured the displacement up to within fifteen degrees of the poles. He brought out the surprising fact that the rotation period of the Sun is there protracted to 38½ days. These remarkable researches were published in 1891.