The famous variable star η Argus, which Sir John Herschel, when at the Cape of Good Hope in 1838, saw involved in dense nebulosity, was in April, 1869, "seen on the bare sky," with the great Melbourne telescope, "the nebula having disappeared for some distance round it." Other changes were noticed in this remarkable nebula. The Melbourne observers saw "three times as many stars as were seen by Herschel." But of course their telescope is much larger--48 inches aperture, compared with Herschel's 20 inches. Prof. E. C. Pickering thinks that the fluctuations of light of the well-known variable star R Coronæ (in the Northern Crown), "are unlike those of any known variable." This very curious object--one of the most curious in the heavens--sometimes remains for many months almost constant in brightness (just visible to the naked eye), and then rapidly fades in light by several magnitudes! Thus its changes of light in April and May, 1905, were as follows:-- 1905, April 1 6·0 magnitude " 11 7·3 " " 12 8·4 " May 1 11·4 " " 7 12·5 " Thus between April 1 and May 1, its light was reduced by over 5 magnitudes. In other words, the light of the star on May 1 was reduced to less than one-hundredth of its light on April 1. If our sun were to behave in this way nearly all life would soon be destroyed on the face of the earth. M. H. E. Lau finds that the short-period variable star δ Cephei varies slightly in colour as well as in light, and that the colour curve is parallel to the light curve. Near the minimum of light the colour is reddish yellow, almost as red as ζ Cephei; a day later it is pure yellow, and of about the same colour as the neighbouring ε Cephei.[332] But it would not be easy to fully establish such slight variations of tint. A remarkably bright maximum of the famous variable Mira Ceti occurred in 1906. In December of that year it was fully 2nd magnitude. The present writer estimated it 1·8, or nearly equal to the brightest on record--1·7 observed by Sir William Herschel and Wargentin in the year 1779. From photographs of the spectrum taken by Mr. Slipher at the Lowell Observatory in 1907, he finds strong indications of the presence of the rather rare element vanadium in the star's surroundings. Prof. Campbell finds with the Mills spectrograph attached to the great 36-inch telescope of the Lick Observatory that Mira is receding from the earth at the apparently constant velocity of about 38 miles a second.[333] This, of course, has nothing to do with the variation in the star's light. Prof. Campbell failed to see any trace of the green line of hydrogen in the star's spectrum, while two other lines of the hydrogen series "glowed with singular intensity."